Struct ArcStr 

pub struct ArcStr(/* private fields */);

A better atomically-reference counted string type.

Benefits of ArcStr over Arc<str>

• It’s possible to create a const ArcStr from a literal via the arcstr::literal! macro. This is probably the killer feature, to be honest.

  These “static” ArcStrs are zero cost, take no heap allocation, and don’t even need to perform atomic reads/writes when being cloned or dropped (nor at any other time).

  They even get stored in the read-only memory of your executable, which can be beneficial for performance and memory usage. (In theory your linker may even dedupe these for you, but usually not)

• ArcStrs from arcstr::literal! can be turned into &'static str safely at any time using ArcStr::as_static. (This returns an Option, which is None if the ArcStr was not static)

• This should be unsurprising given the literal functionality, but ArcStr::new is able to be a const function.

• ArcStr is thin, e.g. only a single pointer. Great for cases where you want to keep the data structure lightweight or need to do some FFI stuff with it.

• ArcStr is totally immutable. No need to lose sleep because you’re afraid of code which thinks it has a right to mutate your Arcs just because it holds the only reference…

• Lower reference counting operations are lower overhead because we don’t support Weak references. This can be a drawback for some use cases, but improves performance for the common case of no-weak-refs.

What does “zero-cost literals” mean?

In a few places I call the literal arcstrs “zero-cost”. No overhead most accesses accesses (aside from stuff like as_static which obviously requires it). and it imposes a extra branch in both clone and drop.

This branch in clone/drop is not on the result of an atomic load, and is just a normal memory read. This is actually what allows literal/static ArcStrs to avoid needing to perform any atomic operations in those functions, which seems likely more than cover the cost.

(Additionally, it’s almost certain that in the future we’ll be able to reduce the synchronization required for atomic instructions. This is due to our guarantee of immutability and lack of support for Weak.)

Usage

As a const

The big unique feature of ArcStr is the ability to create static/const ArcStrs. (See the macro docs or the feature overview

const WOW: ArcStr = arcstr::literal!("cool robot!");
assert_eq!(WOW, "cool robot!");

As a str

(This is not unique to ArcStr, but is a frequent source of confusion I’ve seen): ArcStr implements Deref<Target = str>, and so all functions and methods from str work on it, even though we don’t expose them on ArcStr directly.

let s = ArcStr::from("something");
// These go through `Deref`, so they work even though
// there is no `ArcStr::eq_ignore_ascii_case` function
assert!(s.eq_ignore_ascii_case("SOMETHING"));

Additionally, &ArcStr can be passed to any function which accepts &str. For example:

fn accepts_str(s: &str) {
    // s...
}

let test_str: ArcStr = "test".into();
// This works even though `&test_str` is normally an `&ArcStr`
accepts_str(&test_str);

// Of course, this works for functionality from the standard library as well.
let test_but_loud = ArcStr::from("TEST");
assert!(test_str.eq_ignore_ascii_case(&test_but_loud));

Implementations

impl ArcStr

pub const fn new() -> ArcStr

Construct a new empty string.

Examples

let s = ArcStr::new();
assert_eq!(s, "");

pub fn try_alloc(copy_from: &str) -> Option<ArcStr>

Attempt to copy the provided string into a newly allocated ArcStr, but return None if we cannot allocate the required memory.

Examples

let some_big_str = "please pretend this is a very long string";
if let Some(s) = ArcStr::try_alloc(some_big_str) {
    do_stuff_with(s);
} else {
    // Complain about allocation failure, somehow.
}

pub unsafe fn try_init_with_unchecked<F>( n: usize, initializer: F, ) -> Option<ArcStr>

where F: FnOnce(&mut [MaybeUninit<u8>]),

Attempt to allocate memory for an ArcStr of length n, and use the provided callback to fully initialize the provided buffer with valid UTF-8 text.

This function returns None if memory allocation fails, see ArcStr::init_with_unchecked for a version which calls handle_alloc_error.

Safety

The provided initializer callback must fully initialize the provided buffer with valid UTF-8 text.

Examples

let arcstr = unsafe {
    ArcStr::try_init_with_unchecked(10, |s: &mut [MaybeUninit<u8>]| {
        s.fill(MaybeUninit::new(b'a'));
    }).unwrap()
};
assert_eq!(arcstr, "aaaaaaaaaa")

pub unsafe fn init_with_unchecked<F>(n: usize, initializer: F) -> ArcStr

where F: FnOnce(&mut [MaybeUninit<u8>]),

Allocate memory for an ArcStr of length n, and use the provided callback to fully initialize the provided buffer with valid UTF-8 text.

This function calls handle_alloc_error if memory allocation fails, see ArcStr::try_init_with_unchecked for a version which returns None

Safety

The provided initializer callback must fully initialize the provided buffer with valid UTF-8 text.

Examples

let arcstr = unsafe {
    ArcStr::init_with_unchecked(10, |s: &mut [MaybeUninit<u8>]| {
        s.fill(MaybeUninit::new(b'a'));
    })
};
assert_eq!(arcstr, "aaaaaaaaaa")

pub fn init_with<F>(n: usize, initializer: F) -> Result<ArcStr, Utf8Error>

where F: FnOnce(&mut [u8]),

Attempt to allocate memory for an ArcStr of length n, and use the provided callback to initialize the provided (initially-zeroed) buffer with valid UTF-8 text.

Note: This function is provided with a zeroed buffer, and performs UTF-8 validation after calling the initializer. While both of these are fast operations, some high-performance use cases will be better off using ArcStr::try_init_with_unchecked as the building block.

Errors

The provided initializer callback must initialize the provided buffer with valid UTF-8 text, or a UTF-8 error will be returned.

Examples

let s = ArcStr::init_with(5, |slice| {
    slice
        .iter_mut()
        .zip(b'0'..b'5')
        .for_each(|(db, sb)| *db = sb);
}).unwrap();
assert_eq!(s, "01234");

pub fn as_str(&self) -> &str

Extract a string slice containing our data.

Note: This is an equivalent to our Deref implementation, but can be more readable than &*s in the cases where a manual invocation of Deref would be required.

Examples

let s = ArcStr::from("abc");
assert_eq!(s.as_str(), "abc");

pub fn len(&self) -> usize

Returns the length of this ArcStr in bytes.

Examples

let a = ArcStr::from("foo");
assert_eq!(a.len(), 3);

pub fn is_empty(&self) -> bool

Returns true if this ArcStr is empty.

Examples

assert!(!ArcStr::from("foo").is_empty());
assert!(ArcStr::new().is_empty());

pub fn to_string(&self) -> String

Convert us to a std::string::String.

This is provided as an inherent method to avoid needing to route through the Display machinery, but is equivalent to ToString::to_string.

Examples

let s = ArcStr::from("abc");
assert_eq!(s.to_string(), "abc");

pub fn as_bytes(&self) -> &[u8]

Extract a byte slice containing the string’s data.

Examples

let foobar = ArcStr::from("foobar");
assert_eq!(foobar.as_bytes(), b"foobar");

pub fn into_raw(this: ArcStr) -> NonNull<()>

Return the raw pointer this ArcStr wraps, for advanced use cases.

Note that in addition to the NonNull constraint expressed in the type signature, we also guarantee the pointer has an alignment of at least 8 bytes, even on platforms where a lower alignment would be acceptable.

Examples

let s = ArcStr::from("abcd");
let p = ArcStr::into_raw(s);
// Some time later...
let s = unsafe { ArcStr::from_raw(p) };
assert_eq!(s, "abcd");

pub unsafe fn from_raw(ptr: NonNull<()>) -> ArcStr

The opposite version of Self::into_raw. Still intended only for advanced use cases.

Safety

This function must be used on a valid pointer returned from ArcStr::into_raw. Additionally, you must ensure that a given ArcStr instance is only dropped once.

Examples

let s = ArcStr::from("abcd");
let p = ArcStr::into_raw(s);
// Some time later...
let s = unsafe { ArcStr::from_raw(p) };
assert_eq!(s, "abcd");

pub fn ptr_eq(lhs: &ArcStr, rhs: &ArcStr) -> bool

Returns true if the two ArcStrs point to the same allocation.

Note that functions like PartialEq check this already, so there’s no performance benefit to doing something like ArcStr::ptr_eq(&a1, &a2) || (a1 == a2).

Caveat: consts aren’t guaranteed to only occur in an executable a single time, and so this may be non-deterministic for ArcStr defined in a const with arcstr::literal!, unless one was created by a clone() on the other.

Examples

use arcstr::ArcStr;

let foobar = ArcStr::from("foobar");
let same_foobar = foobar.clone();
let other_foobar = ArcStr::from("foobar");
assert!(ArcStr::ptr_eq(&foobar, &same_foobar));
assert!(!ArcStr::ptr_eq(&foobar, &other_foobar));

const YET_AGAIN_A_DIFFERENT_FOOBAR: ArcStr = arcstr::literal!("foobar");
let strange_new_foobar = YET_AGAIN_A_DIFFERENT_FOOBAR.clone();
let wild_blue_foobar = strange_new_foobar.clone();
assert!(ArcStr::ptr_eq(&strange_new_foobar, &wild_blue_foobar));

pub fn strong_count(this: &ArcStr) -> Option<usize>

Returns the number of references that exist to this ArcStr. If this is a static ArcStr (For example, one from arcstr::literal!), returns None.

Despite the difference in return type, this is named to match the method from the stdlib’s Arc: Arc::strong_count.

If you aren’t sure how to handle static ArcStr in the context of this return value, ArcStr::strong_count(&s).unwrap_or(usize::MAX) is frequently reasonable.

Safety

This method by itself is safe, but using it correctly requires extra care. Another thread can change the strong count at any time, including potentially between calling this method and acting on the result.

However, it may never change from None to Some or from Some to None for a given ArcStr — whether or not it is static is determined at construction, and never changes.

Examples

Dynamic ArcStr

let foobar = ArcStr::from("foobar");
assert_eq!(Some(1), ArcStr::strong_count(&foobar));
let also_foobar = ArcStr::clone(&foobar);
assert_eq!(Some(2), ArcStr::strong_count(&foobar));
assert_eq!(Some(2), ArcStr::strong_count(&also_foobar));

Static ArcStr

let baz = arcstr::literal!("baz");
assert_eq!(None, ArcStr::strong_count(&baz));
// Similarly:
assert_eq!(None, ArcStr::strong_count(&ArcStr::default()));

pub fn leak(&self) -> &'static str

Convert the ArcStr into a “static” ArcStr, even if it was originally created from runtime values. The &'static str is returned.

This is useful if you want to use ArcStr::as_static or ArcStr::is_static on a value only known at runtime.

If the ArcStr is already static, then this is a noop.

Caveats

Calling this function on an ArcStr will cause us to never free it, thus leaking it’s memory. Doing this excessively can lead to problems.

Examples

let s = ArcStr::from("foobar");
assert!(!ArcStr::is_static(&s));
assert!(ArcStr::as_static(&s).is_none());

let leaked: &'static str = s.leak();
assert_eq!(leaked, s);
assert!(ArcStr::is_static(&s));
assert_eq!(ArcStr::as_static(&s), Some("foobar"));

pub fn is_static(this: &ArcStr) -> bool

Returns true if this is a “static” ArcStr. For example, if it was created from a call to arcstr::literal!), returned by ArcStr::new, etc.

Static ArcStrs can be converted to &'static str for free using ArcStr::as_static, without leaking memory — they’re static constants in the program (somewhere).

Examples

const STATIC: ArcStr = arcstr::literal!("Electricity!");
assert!(ArcStr::is_static(&STATIC));

let still_static = arcstr::literal!("Shocking!");
assert!(ArcStr::is_static(&still_static));
assert!(
    ArcStr::is_static(&still_static.clone()),
    "Cloned statics are still static"
);

let nonstatic = ArcStr::from("Grounded...");
assert!(!ArcStr::is_static(&nonstatic));

pub fn as_static(this: &ArcStr) -> Option<&'static str>

Returns true if this is a “static”/"literal" ArcStr. For example, if it was created from a call to literal!), returned by ArcStr::new, etc.

Static ArcStrs can be converted to &'static str for free using ArcStr::as_static, without leaking memory — they’re static constants in the program (somewhere).

Examples

const STATIC: ArcStr = arcstr::literal!("Electricity!");
assert_eq!(ArcStr::as_static(&STATIC), Some("Electricity!"));

// Note that they don't have to be consts, just made using `literal!`:
let still_static = arcstr::literal!("Shocking!");
assert_eq!(ArcStr::as_static(&still_static), Some("Shocking!"));
// Cloning a static still produces a static.
assert_eq!(ArcStr::as_static(&still_static.clone()), Some("Shocking!"));

// But it won't work for strings from other sources.
let nonstatic = ArcStr::from("Grounded...");
assert_eq!(ArcStr::as_static(&nonstatic), None);

pub fn substr(&self, range: impl RangeBounds<usize>) -> Substr

feature = "substr" Returns a substr of self over the given range.

Examples

use arcstr::{ArcStr, Substr};

let a = ArcStr::from("abcde");
let b: Substr = a.substr(2..);

assert_eq!(b, "cde");

Panics

If any of the following are untrue, we panic

• range.start() <= range.end()
• range.end() <= self.len()
• self.is_char_boundary(start) && self.is_char_boundary(end)
• These can be conveniently verified in advance using self.get(start..end).is_some() if needed.

pub fn substr_from(&self, substr: &str) -> Substr

feature = "substr" Returns a Substr of self over the given &str.

It is not rare to end up with a &str which holds a view into a ArcStr’s backing data. A common case is when using functionality that takes and returns &str and are entirely unaware of arcstr, for example: str::trim().

This function allows you to reconstruct a Substr from a &str which is a view into this ArcStr’s backing string.

Examples

use arcstr::{ArcStr, Substr};
let text = ArcStr::from("   abc");
let trimmed = text.trim();
let substr: Substr = text.substr_from(trimmed);
assert_eq!(substr, "abc");
// for illustration
assert!(ArcStr::ptr_eq(substr.parent(), &text));
assert_eq!(substr.range(), 3..6);

Panics

Panics if substr isn’t a view into our memory.

Also panics if substr is a view into our memory but is >= u32::MAX bytes away from our start, if we’re a 64-bit machine and substr-usize-indices is not enabled.

pub fn try_substr_from(&self, substr: &str) -> Option<Substr>

feature = "substr" If possible, returns a Substr of self over the given &str.

This is a fallible version of ArcStr::substr_from.

It is not rare to end up with a &str which holds a view into a ArcStr’s backing data. A common case is when using functionality that takes and returns &str and are entirely unaware of arcstr, for example: str::trim().

This function allows you to reconstruct a Substr from a &str which is a view into this ArcStr’s backing string.

Examples

use arcstr::{ArcStr, Substr};
let text = ArcStr::from("   abc");
let trimmed = text.trim();
let substr: Option<Substr> = text.try_substr_from(trimmed);
assert_eq!(substr.unwrap(), "abc");
// `&str`s not derived from `self` will return None.
let not_substr = text.try_substr_from("abc");
assert!(not_substr.is_none());

Panics

Panics if substr is a view into our memory but is >= u32::MAX bytes away from our start, if we’re a 64-bit machine and substr-usize-indices is not enabled.

pub fn try_substr_using(&self, f: impl FnOnce(&str) -> &str) -> Option<Substr>

feature = "substr" Compute a derived &str a function of &str => &str, and produce a Substr of the result if possible.

The function may return either a derived string, or any empty string.

This function is mainly a wrapper around ArcStr::try_substr_from. If you’re coming to arcstr from the shared_string crate, this is the moral equivalent of the slice_with function.

Examples

use arcstr::{ArcStr, Substr};
let text = ArcStr::from("   abc");
let trimmed: Option<Substr> = text.try_substr_using(str::trim);
assert_eq!(trimmed.unwrap(), "abc");
let other = text.try_substr_using(|_s| "different string!");
assert_eq!(other, None);
// As a special case, this is allowed.
let empty = text.try_substr_using(|_s| "");
assert_eq!(empty.unwrap(), "");

pub fn substr_using(&self, f: impl FnOnce(&str) -> &str) -> Substr

feature = "substr" Compute a derived &str a function of &str => &str, and produce a Substr of the result.

The function may return either a derived string, or any empty string. Returning anything else will result in a panic.

This function is mainly a wrapper around ArcStr::try_substr_from. If you’re coming to arcstr from the shared_string crate, this is the likely closest to the slice_with_unchecked function, but this panics instead of UB on dodginess.

Examples

use arcstr::{ArcStr, Substr};
let text = ArcStr::from("   abc");
let trimmed: Substr = text.substr_using(str::trim);
assert_eq!(trimmed, "abc");
// As a special case, this is allowed.
let empty = text.substr_using(|_s| "");
assert_eq!(empty, "");

pub fn try_repeat(source: &str, n: usize) -> Option<ArcStr>

Creates an ArcStr by repeating the source string n times

Errors

This function returns an error if the capacity overflows or allocation fails.

Examples

use arcstr::ArcStr;

let source = "A";
let repeated = ArcStr::try_repeat(source, 10);
assert_eq!(repeated.unwrap(), "AAAAAAAAAA");

pub fn repeat(source: &str, n: usize) -> ArcStr

Creates an ArcStr by repeating the source string n times

Panics

This function panics if the capacity overflows, see try_repeat if this is undesirable.

Examples

Basic usage:

use arcstr::ArcStr;

let source = "A";
let repeated = ArcStr::repeat(source, 10);
assert_eq!(repeated, "AAAAAAAAAA");

A panic upon overflow:

// this will panic at runtime
let huge = ArcStr::repeat("A", usize::MAX);

Methods from Deref<Target = str>

pub fn len(&self) -> usize

Returns the length of self.

This length is in bytes, not chars or graphemes. In other words, it might not be what a human considers the length of the string.

Examples

let len = "foo".len();
assert_eq!(3, len);

assert_eq!("ƒoo".len(), 4); // fancy f!
assert_eq!("ƒoo".chars().count(), 3);

pub fn is_empty(&self) -> bool

Returns true if self has a length of zero bytes.

Examples

let s = "";
assert!(s.is_empty());

let s = "not empty";
assert!(!s.is_empty());

pub fn is_char_boundary(&self, index: usize) -> bool

Checks that index-th byte is the first byte in a UTF-8 code point sequence or the end of the string.

The start and end of the string (when index == self.len()) are considered to be boundaries.

Returns false if index is greater than self.len().

Examples

let s = "Löwe 老虎 Léopard";
assert!(s.is_char_boundary(0));
// start of `老`
assert!(s.is_char_boundary(6));
assert!(s.is_char_boundary(s.len()));

// second byte of `ö`
assert!(!s.is_char_boundary(2));

// third byte of `老`
assert!(!s.is_char_boundary(8));

pub fn floor_char_boundary(&self, index: usize) -> usize

Finds the closest x not exceeding index where is_char_boundary(x) is true.

This method can help you truncate a string so that it’s still valid UTF-8, but doesn’t exceed a given number of bytes. Note that this is done purely at the character level and can still visually split graphemes, even though the underlying characters aren’t split. For example, the emoji 🧑‍🔬 (scientist) could be split so that the string only includes 🧑 (person) instead.

Examples

let s = "❤️🧡💛💚💙💜";
assert_eq!(s.len(), 26);
assert!(!s.is_char_boundary(13));

let closest = s.floor_char_boundary(13);
assert_eq!(closest, 10);
assert_eq!(&s[..closest], "❤️🧡");

pub fn ceil_char_boundary(&self, index: usize) -> usize

Finds the closest x not below index where is_char_boundary(x) is true.

If index is greater than the length of the string, this returns the length of the string.

This method is the natural complement to floor_char_boundary. See that method for more details.

Examples

let s = "❤️🧡💛💚💙💜";
assert_eq!(s.len(), 26);
assert!(!s.is_char_boundary(13));

let closest = s.ceil_char_boundary(13);
assert_eq!(closest, 14);
assert_eq!(&s[..closest], "❤️🧡💛");

pub fn as_bytes(&self) -> &[u8]

Converts a string slice to a byte slice. To convert the byte slice back into a string slice, use the from_utf8 function.

Examples

let bytes = "bors".as_bytes();
assert_eq!(b"bors", bytes);

pub fn as_ptr(&self) -> *const u8

Converts a string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a u8. This pointer will be pointing to the first byte of the string slice.

The caller must ensure that the returned pointer is never written to. If you need to mutate the contents of the string slice, use as_mut_ptr.

Examples

let s = "Hello";
let ptr = s.as_ptr();

pub fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output>

where I: SliceIndex<str>,

Returns a subslice of str.

This is the non-panicking alternative to indexing the str. Returns None whenever equivalent indexing operation would panic.

Examples

let v = String::from("🗻∈🌏");

assert_eq!(Some("🗻"), v.get(0..4));

// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());

// out of bounds
assert!(v.get(..42).is_none());

pub unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Output

where I: SliceIndex<str>,

Returns an unchecked subslice of str.

This is the unchecked alternative to indexing the str.

Safety

Callers of this function are responsible that these preconditions are satisfied:

• The starting index must not exceed the ending index;
• Indexes must be within bounds of the original slice;
• Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str type.

Examples

let v = "🗻∈🌏";
unsafe {
    assert_eq!("🗻", v.get_unchecked(0..4));
    assert_eq!("∈", v.get_unchecked(4..7));
    assert_eq!("🌏", v.get_unchecked(7..11));
}

pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str

👎Deprecated since 1.29.0: use get_unchecked(begin..end) instead

Creates a string slice from another string slice, bypassing safety checks.

This is generally not recommended, use with caution! For a safe alternative see str and Index.

This new slice goes from begin to end, including begin but excluding end.

To get a mutable string slice instead, see the slice_mut_unchecked method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

• begin must not exceed end.
• begin and end must be byte positions within the string slice.
• begin and end must lie on UTF-8 sequence boundaries.

Examples

let s = "Löwe 老虎 Léopard";

unsafe {
    assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
}

let s = "Hello, world!";

unsafe {
    assert_eq!("world", s.slice_unchecked(7, 12));
}

pub fn split_at(&self, mid: usize) -> (&str, &str)

Divides one string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get mutable string slices instead, see the split_at_mut method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is past the end of the last code point of the string slice. For a non-panicking alternative see split_at_checked.

Examples

let s = "Per Martin-Löf";

let (first, last) = s.split_at(3);

assert_eq!("Per", first);
assert_eq!(" Martin-Löf", last);

pub fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)>

Divides one string slice into two at an index.

The argument, mid, should be a valid byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point. The method returns None if that’s not the case.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get mutable string slices instead, see the split_at_mut_checked method.

Examples

let s = "Per Martin-Löf";

let (first, last) = s.split_at_checked(3).unwrap();
assert_eq!("Per", first);
assert_eq!(" Martin-Löf", last);

assert_eq!(None, s.split_at_checked(13));  // Inside “ö”
assert_eq!(None, s.split_at_checked(16));  // Beyond the string length

pub fn chars(&self) -> Chars<'_>

Returns an iterator over the chars of a string slice.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns such an iterator.

It’s important to remember that char represents a Unicode Scalar Value, and might not match your idea of what a ‘character’ is. Iteration over grapheme clusters may be what you actually want. This functionality is not provided by Rust’s standard library, check crates.io instead.

Examples

Basic usage:

let word = "goodbye";

let count = word.chars().count();
assert_eq!(7, count);

let mut chars = word.chars();

assert_eq!(Some('g'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('d'), chars.next());
assert_eq!(Some('b'), chars.next());
assert_eq!(Some('y'), chars.next());
assert_eq!(Some('e'), chars.next());

assert_eq!(None, chars.next());

Remember, chars might not match your intuition about characters:

let y = "y̆";

let mut chars = y.chars();

assert_eq!(Some('y'), chars.next()); // not 'y̆'
assert_eq!(Some('\u{0306}'), chars.next());

assert_eq!(None, chars.next());

pub fn char_indices(&self) -> CharIndices<'_>

Returns an iterator over the chars of a string slice, and their positions.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns an iterator of both these chars, as well as their byte positions.

The iterator yields tuples. The position is first, the char is second.

Examples

Basic usage:

let word = "goodbye";

let count = word.char_indices().count();
assert_eq!(7, count);

let mut char_indices = word.char_indices();

assert_eq!(Some((0, 'g')), char_indices.next());
assert_eq!(Some((1, 'o')), char_indices.next());
assert_eq!(Some((2, 'o')), char_indices.next());
assert_eq!(Some((3, 'd')), char_indices.next());
assert_eq!(Some((4, 'b')), char_indices.next());
assert_eq!(Some((5, 'y')), char_indices.next());
assert_eq!(Some((6, 'e')), char_indices.next());

assert_eq!(None, char_indices.next());

Remember, chars might not match your intuition about characters:

let yes = "y̆es";

let mut char_indices = yes.char_indices();

assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
assert_eq!(Some((1, '\u{0306}')), char_indices.next());

// note the 3 here - the previous character took up two bytes
assert_eq!(Some((3, 'e')), char_indices.next());
assert_eq!(Some((4, 's')), char_indices.next());

assert_eq!(None, char_indices.next());

pub fn bytes(&self) -> Bytes<'_>

Returns an iterator over the bytes of a string slice.

As a string slice consists of a sequence of bytes, we can iterate through a string slice by byte. This method returns such an iterator.

Examples

let mut bytes = "bors".bytes();

assert_eq!(Some(b'b'), bytes.next());
assert_eq!(Some(b'o'), bytes.next());
assert_eq!(Some(b'r'), bytes.next());
assert_eq!(Some(b's'), bytes.next());

assert_eq!(None, bytes.next());

pub fn split_whitespace(&self) -> SplitWhitespace<'_>

Splits a string slice by whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of whitespace.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space. If you only want to split on ASCII whitespace instead, use split_ascii_whitespace.

Examples

Basic usage:

let mut iter = "A few words".split_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());

All kinds of whitespace are considered:

let mut iter = " Mary   had\ta\u{2009}little  \n\t lamb".split_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());

If the string is empty or all whitespace, the iterator yields no string slices:

assert_eq!("".split_whitespace().next(), None);
assert_eq!("   ".split_whitespace().next(), None);

pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace<'_>

Splits a string slice by ASCII whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of ASCII whitespace.

This uses the same definition as char::is_ascii_whitespace. To split by Unicode Whitespace instead, use split_whitespace.

Examples

Basic usage:

let mut iter = "A few words".split_ascii_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());

Various kinds of ASCII whitespace are considered (see char::is_ascii_whitespace):

let mut iter = " Mary   had\ta little  \n\t lamb".split_ascii_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());

If the string is empty or all ASCII whitespace, the iterator yields no string slices:

assert_eq!("".split_ascii_whitespace().next(), None);
assert_eq!("   ".split_ascii_whitespace().next(), None);

pub fn lines(&self) -> Lines<'_>

Returns an iterator over the lines of a string, as string slices.

Lines are split at line endings that are either newlines (\n) or sequences of a carriage return followed by a line feed (\r\n).

Line terminators are not included in the lines returned by the iterator.

Note that any carriage return (\r) not immediately followed by a line feed (\n) does not split a line. These carriage returns are thereby included in the produced lines.

The final line ending is optional. A string that ends with a final line ending will return the same lines as an otherwise identical string without a final line ending.

Examples

Basic usage:

let text = "foo\r\nbar\n\nbaz\r";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
// Trailing carriage return is included in the last line
assert_eq!(Some("baz\r"), lines.next());

assert_eq!(None, lines.next());

The final line does not require any ending:

let text = "foo\nbar\n\r\nbaz";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());

pub fn lines_any(&self) -> LinesAny<'_>

👎Deprecated since 1.4.0: use lines() instead now

Returns an iterator over the lines of a string.

pub fn encode_utf16(&self) -> EncodeUtf16<'_>

Returns an iterator of u16 over the string encoded as native endian UTF-16 (without byte-order mark).

Examples

let text = "Zażółć gęślą jaźń";

let utf8_len = text.len();
let utf16_len = text.encode_utf16().count();

assert!(utf16_len <= utf8_len);

pub fn contains<P>(&self, pat: P) -> bool

where P: Pattern,

Returns true if the given pattern matches a sub-slice of this string slice.

Returns false if it does not.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

let bananas = "bananas";

assert!(bananas.contains("nana"));
assert!(!bananas.contains("apples"));

pub fn starts_with<P>(&self, pat: P) -> bool

where P: Pattern,

Returns true if the given pattern matches a prefix of this string slice.

Returns false if it does not.

The pattern can be a &str, in which case this function will return true if the &str is a prefix of this string slice.

The pattern can also be a char, a slice of chars, or a function or closure that determines if a character matches. These will only be checked against the first character of this string slice. Look at the second example below regarding behavior for slices of chars.

Examples

let bananas = "bananas";

assert!(bananas.starts_with("bana"));
assert!(!bananas.starts_with("nana"));

let bananas = "bananas";

// Note that both of these assert successfully.
assert!(bananas.starts_with(&['b', 'a', 'n', 'a']));
assert!(bananas.starts_with(&['a', 'b', 'c', 'd']));

pub fn ends_with<P>(&self, pat: P) -> bool

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns true if the given pattern matches a suffix of this string slice.

Returns false if it does not.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

let bananas = "bananas";

assert!(bananas.ends_with("anas"));
assert!(!bananas.ends_with("nana"));

pub fn find<P>(&self, pat: P) -> Option<usize>

where P: Pattern,

Returns the byte index of the first character of this string slice that matches the pattern.

Returns None if the pattern doesn’t match.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Simple patterns:

let s = "Löwe 老虎 Léopard Gepardi";

assert_eq!(s.find('L'), Some(0));
assert_eq!(s.find('é'), Some(14));
assert_eq!(s.find("pard"), Some(17));

More complex patterns using point-free style and closures:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.find(char::is_whitespace), Some(5));
assert_eq!(s.find(char::is_lowercase), Some(1));
assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.find(x), None);

pub fn rfind<P>(&self, pat: P) -> Option<usize>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns the byte index for the first character of the last match of the pattern in this string slice.

Returns None if the pattern doesn’t match.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Simple patterns:

let s = "Löwe 老虎 Léopard Gepardi";

assert_eq!(s.rfind('L'), Some(13));
assert_eq!(s.rfind('é'), Some(14));
assert_eq!(s.rfind("pard"), Some(24));

More complex patterns with closures:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.rfind(char::is_whitespace), Some(12));
assert_eq!(s.rfind(char::is_lowercase), Some(20));

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.rfind(x), None);

pub fn split<P>(&self, pat: P) -> Split<'_, P>

where P: Pattern,

Returns an iterator over substrings of this string slice, separated by characters matched by a pattern.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

If there are no matches the full string slice is returned as the only item in the iterator.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);

let v: Vec<&str> = "".split('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
assert_eq!(v, ["lion", "", "tiger", "leopard"]);

let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

let v: Vec<&str> = "AABBCC".split("DD").collect();
assert_eq!(v, ["AABBCC"]);

let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
assert_eq!(v, ["abc", "def", "ghi"]);

let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

If the pattern is a slice of chars, split on each occurrence of any of the characters:

let v: Vec<&str> = "2020-11-03 23:59".split(&['-', ' ', ':', '@'][..]).collect();
assert_eq!(v, ["2020", "11", "03", "23", "59"]);

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "def", "ghi"]);

If a string contains multiple contiguous separators, you will end up with empty strings in the output:

let x = "||||a||b|c".to_string();
let d: Vec<_> = x.split('|').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);

Contiguous separators are separated by the empty string.

let x = "(///)".to_string();
let d: Vec<_> = x.split('/').collect();

assert_eq!(d, &["(", "", "", ")"]);

Separators at the start or end of a string are neighbored by empty strings.

let d: Vec<_> = "010".split("0").collect();
assert_eq!(d, &["", "1", ""]);

When the empty string is used as a separator, it separates every character in the string, along with the beginning and end of the string.

let f: Vec<_> = "rust".split("").collect();
assert_eq!(f, &["", "r", "u", "s", "t", ""]);

Contiguous separators can lead to possibly surprising behavior when whitespace is used as the separator. This code is correct:

let x = "    a  b c".to_string();
let d: Vec<_> = x.split(' ').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);

It does not give you:

assert_eq!(d, &["a", "b", "c"]);

Use split_whitespace for this behavior.

pub fn split_inclusive<P>(&self, pat: P) -> SplitInclusive<'_, P>

where P: Pattern,

Returns an iterator over substrings of this string slice, separated by characters matched by a pattern.

Differs from the iterator produced by split in that split_inclusive leaves the matched part as the terminator of the substring.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb."
    .split_inclusive('\n').collect();
assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb."]);

If the last element of the string is matched, that element will be considered the terminator of the preceding substring. That substring will be the last item returned by the iterator.

let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb.\n"
    .split_inclusive('\n').collect();
assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb.\n"]);

pub fn rsplit<P>(&self, pat: P) -> RSplit<'_, P>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns an iterator over substrings of the given string slice, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the split method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);

let v: Vec<&str> = "".rsplit('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
assert_eq!(v, ["leopard", "tiger", "", "lion"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
assert_eq!(v, ["leopard", "tiger", "lion"]);

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "def", "abc"]);

pub fn split_terminator<P>(&self, pat: P) -> SplitTerminator<'_, P>

where P: Pattern,

Returns an iterator over substrings of the given string slice, separated by characters matched by a pattern.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Equivalent to split, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit_terminator method can be used.

Examples

let v: Vec<&str> = "A.B.".split_terminator('.').collect();
assert_eq!(v, ["A", "B"]);

let v: Vec<&str> = "A..B..".split_terminator(".").collect();
assert_eq!(v, ["A", "", "B", ""]);

let v: Vec<&str> = "A.B:C.D".split_terminator(&['.', ':'][..]).collect();
assert_eq!(v, ["A", "B", "C", "D"]);

pub fn rsplit_terminator<P>(&self, pat: P) -> RSplitTerminator<'_, P>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns an iterator over substrings of self, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Equivalent to split, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be double ended if a forward/reverse search yields the same elements.

For iterating from the front, the split_terminator method can be used.

Examples

let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
assert_eq!(v, ["B", "A"]);

let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
assert_eq!(v, ["", "B", "", "A"]);

let v: Vec<&str> = "A.B:C.D".rsplit_terminator(&['.', ':'][..]).collect();
assert_eq!(v, ["D", "C", "B", "A"]);

pub fn splitn<P>(&self, n: usize, pat: P) -> SplitN<'_, P>

where P: Pattern,

Returns an iterator over substrings of the given string slice, separated by a pattern, restricted to returning at most n items.

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

If the pattern allows a reverse search, the rsplitn method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
assert_eq!(v, ["Mary", "had", "a little lambda"]);

let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
assert_eq!(v, ["lion", "", "tigerXleopard"]);

let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
assert_eq!(v, ["abcXdef"]);

let v: Vec<&str> = "".splitn(1, 'X').collect();
assert_eq!(v, [""]);

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "defXghi"]);

pub fn rsplitn<P>(&self, n: usize, pat: P) -> RSplitN<'_, P>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns an iterator over substrings of this string slice, separated by a pattern, starting from the end of the string, restricted to returning at most n items.

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

For splitting from the front, the splitn method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
assert_eq!(v, ["lamb", "little", "Mary had a"]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
assert_eq!(v, ["leopard", "tiger", "lionX"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
assert_eq!(v, ["leopard", "lion::tiger"]);

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "abc1def"]);

pub fn split_once<P>(&self, delimiter: P) -> Option<(&str, &str)>

where P: Pattern,

Splits the string on the first occurrence of the specified delimiter and returns prefix before delimiter and suffix after delimiter.

Examples

assert_eq!("cfg".split_once('='), None);
assert_eq!("cfg=".split_once('='), Some(("cfg", "")));
assert_eq!("cfg=foo".split_once('='), Some(("cfg", "foo")));
assert_eq!("cfg=foo=bar".split_once('='), Some(("cfg", "foo=bar")));

pub fn rsplit_once<P>(&self, delimiter: P) -> Option<(&str, &str)>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Splits the string on the last occurrence of the specified delimiter and returns prefix before delimiter and suffix after delimiter.

Examples

assert_eq!("cfg".rsplit_once('='), None);
assert_eq!("cfg=foo".rsplit_once('='), Some(("cfg", "foo")));
assert_eq!("cfg=foo=bar".rsplit_once('='), Some(("cfg=foo", "bar")));

pub fn matches<P>(&self, pat: P) -> Matches<'_, P>

where P: Pattern,

Returns an iterator over the disjoint matches of a pattern within the given string slice.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatches method can be used.

Examples

let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
assert_eq!(v, ["1", "2", "3"]);

pub fn rmatches<P>(&self, pat: P) -> RMatches<'_, P>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns an iterator over the disjoint matches of a pattern within this string slice, yielded in reverse order.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the matches method can be used.

Examples

let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
assert_eq!(v, ["3", "2", "1"]);

pub fn match_indices<P>(&self, pat: P) -> MatchIndices<'_, P>

where P: Pattern,

Returns an iterator over the disjoint matches of a pattern within this string slice as well as the index that the match starts at.

For matches of pat within self that overlap, only the indices corresponding to the first match are returned.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatch_indices method can be used.

Examples

let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);

let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
assert_eq!(v, [(1, "abc"), (4, "abc")]);

let v: Vec<_> = "ababa".match_indices("aba").collect();
assert_eq!(v, [(0, "aba")]); // only the first `aba`

pub fn rmatch_indices<P>(&self, pat: P) -> RMatchIndices<'_, P>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns an iterator over the disjoint matches of a pattern within self, yielded in reverse order along with the index of the match.

For matches of pat within self that overlap, only the indices corresponding to the last match are returned.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the match_indices method can be used.

Examples

let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);

let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
assert_eq!(v, [(4, "abc"), (1, "abc")]);

let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
assert_eq!(v, [(2, "aba")]); // only the last `aba`

pub fn trim(&self) -> &str

Returns a string slice with leading and trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space, which includes newlines.

Examples

let s = "\n Hello\tworld\t\n";

assert_eq!("Hello\tworld", s.trim());

pub fn trim_start(&self) -> &str

Returns a string slice with leading whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space, which includes newlines.

Text directionality

A string is a sequence of bytes. start in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

Examples

Basic usage:

let s = "\n Hello\tworld\t\n";
assert_eq!("Hello\tworld\t\n", s.trim_start());

Directionality:

let s = "  English  ";
assert!(Some('E') == s.trim_start().chars().next());

let s = "  עברית  ";
assert!(Some('ע') == s.trim_start().chars().next());

pub fn trim_end(&self) -> &str

Returns a string slice with trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space, which includes newlines.

Text directionality

A string is a sequence of bytes. end in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

Examples

Basic usage:

let s = "\n Hello\tworld\t\n";
assert_eq!("\n Hello\tworld", s.trim_end());

Directionality:

let s = "  English  ";
assert!(Some('h') == s.trim_end().chars().rev().next());

let s = "  עברית  ";
assert!(Some('ת') == s.trim_end().chars().rev().next());

pub fn trim_left(&self) -> &str

👎Deprecated since 1.33.0: superseded by trim_start

Returns a string slice with leading whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. ‘Left’ in this context means the first position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the right side, not the left.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!("Hello\tworld\t", s.trim_left());

Directionality:

let s = "  English";
assert!(Some('E') == s.trim_left().chars().next());

let s = "  עברית";
assert!(Some('ע') == s.trim_left().chars().next());

pub fn trim_right(&self) -> &str

👎Deprecated since 1.33.0: superseded by trim_end

Returns a string slice with trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. ‘Right’ in this context means the last position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the left side, not the right.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!(" Hello\tworld", s.trim_right());

Directionality:

let s = "English  ";
assert!(Some('h') == s.trim_right().chars().rev().next());

let s = "עברית  ";
assert!(Some('ת') == s.trim_right().chars().rev().next());

pub fn trim_matches<P>(&self, pat: P) -> &str

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> DoubleEndedSearcher<'a>,

Returns a string slice with all prefixes and suffixes that match a pattern repeatedly removed.

The pattern can be a char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");

A more complex pattern, using a closure:

assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");

pub fn trim_start_matches<P>(&self, pat: P) -> &str

where P: Pattern,

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. start in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

Examples

assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");

pub fn strip_prefix<P>(&self, prefix: P) -> Option<&str>

where P: Pattern,

Returns a string slice with the prefix removed.

If the string starts with the pattern prefix, returns the substring after the prefix, wrapped in Some. Unlike trim_start_matches, this method removes the prefix exactly once.

If the string does not start with prefix, returns None.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

assert_eq!("foo:bar".strip_prefix("foo:"), Some("bar"));
assert_eq!("foo:bar".strip_prefix("bar"), None);
assert_eq!("foofoo".strip_prefix("foo"), Some("foo"));

pub fn strip_suffix<P>(&self, suffix: P) -> Option<&str>

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns a string slice with the suffix removed.

If the string ends with the pattern suffix, returns the substring before the suffix, wrapped in Some. Unlike trim_end_matches, this method removes the suffix exactly once.

If the string does not end with suffix, returns None.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

assert_eq!("bar:foo".strip_suffix(":foo"), Some("bar"));
assert_eq!("bar:foo".strip_suffix("bar"), None);
assert_eq!("foofoo".strip_suffix("foo"), Some("foo"));

pub fn trim_prefix<P>(&self, prefix: P) -> &str

where P: Pattern,

🔬This is a nightly-only experimental API. (trim_prefix_suffix)

Returns a string slice with the optional prefix removed.

If the string starts with the pattern prefix, returns the substring after the prefix. Unlike strip_prefix, this method always returns &str for easy method chaining, instead of returning Option<&str>.

If the string does not start with prefix, returns the original string unchanged.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

#![feature(trim_prefix_suffix)]

// Prefix present - removes it
assert_eq!("foo:bar".trim_prefix("foo:"), "bar");
assert_eq!("foofoo".trim_prefix("foo"), "foo");

// Prefix absent - returns original string
assert_eq!("foo:bar".trim_prefix("bar"), "foo:bar");

// Method chaining example
assert_eq!("<https://example.com/>".trim_prefix('<').trim_suffix('>'), "https://example.com/");

pub fn trim_suffix<P>(&self, suffix: P) -> &str

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (trim_prefix_suffix)

Returns a string slice with the optional suffix removed.

If the string ends with the pattern suffix, returns the substring before the suffix. Unlike strip_suffix, this method always returns &str for easy method chaining, instead of returning Option<&str>.

If the string does not end with suffix, returns the original string unchanged.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

#![feature(trim_prefix_suffix)]

// Suffix present - removes it
assert_eq!("bar:foo".trim_suffix(":foo"), "bar");
assert_eq!("foofoo".trim_suffix("foo"), "foo");

// Suffix absent - returns original string
assert_eq!("bar:foo".trim_suffix("bar"), "bar:foo");

// Method chaining example
assert_eq!("<https://example.com/>".trim_prefix('<').trim_suffix('>'), "https://example.com/");

pub fn trim_end_matches<P>(&self, pat: P) -> &str

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. end in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_end_matches(x), "12foo1bar");

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");

pub fn trim_left_matches<P>(&self, pat: P) -> &str

where P: Pattern,

👎Deprecated since 1.33.0: superseded by trim_start_matches

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. ‘Left’ in this context means the first position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the right side, not the left.

Examples

assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");

pub fn trim_right_matches<P>(&self, pat: P) -> &str

where P: Pattern, <P as Pattern>::Searcher<'a>: for<'a> ReverseSearcher<'a>,

👎Deprecated since 1.33.0: superseded by trim_end_matches

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. ‘Right’ in this context means the last position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the left side, not the right.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");

pub fn parse<F>(&self) -> Result<F, <F as FromStr>::Err>

where F: FromStr,

Parses this string slice into another type.

Because parse is so general, it can cause problems with type inference. As such, parse is one of the few times you’ll see the syntax affectionately known as the ‘turbofish’: ::<>. This helps the inference algorithm understand specifically which type you’re trying to parse into.

parse can parse into any type that implements the FromStr trait.

Errors

Will return Err if it’s not possible to parse this string slice into the desired type.

Examples

Basic usage:

let four: u32 = "4".parse().unwrap();

assert_eq!(4, four);

Using the ‘turbofish’ instead of annotating four:

let four = "4".parse::<u32>();

assert_eq!(Ok(4), four);

Failing to parse:

let nope = "j".parse::<u32>();

assert!(nope.is_err());

pub fn is_ascii(&self) -> bool

Checks if all characters in this string are within the ASCII range.

Examples

let ascii = "hello!\n";
let non_ascii = "Grüße, Jürgen ❤";

assert!(ascii.is_ascii());
assert!(!non_ascii.is_ascii());

pub fn as_ascii(&self) -> Option<&[AsciiChar]>

🔬This is a nightly-only experimental API. (ascii_char)

If this string slice is_ascii, returns it as a slice of ASCII characters, otherwise returns None.

pub unsafe fn as_ascii_unchecked(&self) -> &[AsciiChar]

🔬This is a nightly-only experimental API. (ascii_char)

Converts this string slice into a slice of ASCII characters, without checking whether they are valid.

Safety

Every character in this string must be ASCII, or else this is UB.

pub fn eq_ignore_ascii_case(&self, other: &str) -> bool

Checks that two strings are an ASCII case-insensitive match.

Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.

Examples

assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));

pub fn trim_ascii_start(&self) -> &str

Returns a string slice with leading ASCII whitespace removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples

assert_eq!(" \t \u{3000}hello world\n".trim_ascii_start(), "\u{3000}hello world\n");
assert_eq!("  ".trim_ascii_start(), "");
assert_eq!("".trim_ascii_start(), "");

pub fn trim_ascii_end(&self) -> &str

Returns a string slice with trailing ASCII whitespace removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples

assert_eq!("\r hello world\u{3000}\n ".trim_ascii_end(), "\r hello world\u{3000}");
assert_eq!("  ".trim_ascii_end(), "");
assert_eq!("".trim_ascii_end(), "");

pub fn trim_ascii(&self) -> &str

Returns a string slice with leading and trailing ASCII whitespace removed.

‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.

Examples

assert_eq!("\r hello world\n ".trim_ascii(), "hello world");
assert_eq!("  ".trim_ascii(), "");
assert_eq!("".trim_ascii(), "");

pub fn escape_debug(&self) -> EscapeDebug<'_>

Returns an iterator that escapes each char in self with char::escape_debug.

Note: only extended grapheme codepoints that begin the string will be escaped.

Examples

As an iterator:

for c in "❤\n!".escape_debug() {
    print!("{c}");
}
println!();

Using println! directly:

println!("{}", "❤\n!".escape_debug());

Both are equivalent to:

println!("❤\\n!");

Using to_string:

assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");

pub fn escape_default(&self) -> EscapeDefault<'_>

Returns an iterator that escapes each char in self with char::escape_default.

Examples

As an iterator:

for c in "❤\n!".escape_default() {
    print!("{c}");
}
println!();

Using println! directly:

println!("{}", "❤\n!".escape_default());

Both are equivalent to:

println!("\\u{{2764}}\\n!");

Using to_string:

assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");

pub fn escape_unicode(&self) -> EscapeUnicode<'_>

Returns an iterator that escapes each char in self with char::escape_unicode.

Examples

As an iterator:

for c in "❤\n!".escape_unicode() {
    print!("{c}");
}
println!();

Using println! directly:

println!("{}", "❤\n!".escape_unicode());

Both are equivalent to:

println!("\\u{{2764}}\\u{{a}}\\u{{21}}");

Using to_string:

assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");

pub fn substr_range(&self, substr: &str) -> Option<Range<usize>>

🔬This is a nightly-only experimental API. (substr_range)

Returns the range that a substring points to.

Returns None if substr does not point within self.

Unlike str::find, this does not search through the string. Instead, it uses pointer arithmetic to find where in the string substr is derived from.

This is useful for extending str::split and similar methods.

Note that this method may return false positives (typically either Some(0..0) or Some(self.len()..self.len())) if substr is a zero-length str that points at the beginning or end of another, independent, str.

Examples

#![feature(substr_range)]

let data = "a, b, b, a";
let mut iter = data.split(", ").map(|s| data.substr_range(s).unwrap());

assert_eq!(iter.next(), Some(0..1));
assert_eq!(iter.next(), Some(3..4));
assert_eq!(iter.next(), Some(6..7));
assert_eq!(iter.next(), Some(9..10));

pub fn as_str(&self) -> &str

🔬This is a nightly-only experimental API. (str_as_str)

Returns the same string as a string slice &str.

This method is redundant when used directly on &str, but it helps dereferencing other string-like types to string slices, for example references to Box<str> or Arc<str>.

pub fn replace<P>(&self, from: P, to: &str) -> String

where P: Pattern,

Replaces all matches of a pattern with another string.

replace creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice.

Examples

let s = "this is old";

assert_eq!("this is new", s.replace("old", "new"));
assert_eq!("than an old", s.replace("is", "an"));

When the pattern doesn’t match, it returns this string slice as String:

let s = "this is old";
assert_eq!(s, s.replace("cookie monster", "little lamb"));

pub fn replacen<P>(&self, pat: P, to: &str, count: usize) -> String

where P: Pattern,

Replaces first N matches of a pattern with another string.

replacen creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice at most count times.

Examples

let s = "foo foo 123 foo";
assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));

When the pattern doesn’t match, it returns this string slice as String:

let s = "this is old";
assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));

pub fn to_lowercase(&self) -> String

Returns the lowercase equivalent of this string slice, as a new String.

‘Lowercase’ is defined according to the terms of the Unicode Derived Core Property Lowercase.

Since some characters can expand into multiple characters when changing the case, this function returns a String instead of modifying the parameter in-place.

Examples

Basic usage:

let s = "HELLO";

assert_eq!("hello", s.to_lowercase());

A tricky example, with sigma:

let sigma = "Σ";

assert_eq!("σ", sigma.to_lowercase());

// but at the end of a word, it's ς, not σ:
let odysseus = "ὈΔΥΣΣΕΎΣ";

assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());

Languages without case are not changed:

let new_year = "农历新年";

assert_eq!(new_year, new_year.to_lowercase());

pub fn to_uppercase(&self) -> String

Returns the uppercase equivalent of this string slice, as a new String.

‘Uppercase’ is defined according to the terms of the Unicode Derived Core Property Uppercase.

Since some characters can expand into multiple characters when changing the case, this function returns a String instead of modifying the parameter in-place.

Examples

Basic usage:

let s = "hello";

assert_eq!("HELLO", s.to_uppercase());

Scripts without case are not changed:

let new_year = "农历新年";

assert_eq!(new_year, new_year.to_uppercase());

One character can become multiple:

let s = "tschüß";

assert_eq!("TSCHÜSS", s.to_uppercase());

pub fn repeat(&self, n: usize) -> String

Creates a new String by repeating a string n times.

Panics

This function will panic if the capacity would overflow.

Examples

Basic usage:

assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));

A panic upon overflow:

// this will panic at runtime
let huge = "0123456789abcdef".repeat(usize::MAX);

pub fn to_ascii_uppercase(&self) -> String

Returns a copy of this string where each character is mapped to its ASCII upper case equivalent.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

To uppercase ASCII characters in addition to non-ASCII characters, use to_uppercase.

Examples

let s = "Grüße, Jürgen ❤";

assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());

pub fn to_ascii_lowercase(&self) -> String

Returns a copy of this string where each character is mapped to its ASCII lower case equivalent.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

To lowercase ASCII characters in addition to non-ASCII characters, use to_lowercase.

Examples

let s = "Grüße, Jürgen ❤";

assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());

Trait Implementations

impl AsRef<[u8]> for ArcStr

fn as_ref(&self) -> &[u8]

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<str> for ArcStr

fn as_ref(&self) -> &str

Converts this type into a shared reference of the (usually inferred) input type.

impl Borrow<str> for ArcStr

fn borrow(&self) -> &str

Immutably borrows from an owned value.

impl Clone for ArcStr

fn clone(&self) -> ArcStr

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ArcStr

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for ArcStr

fn default() -> ArcStr

Returns the “default value” for a type.

impl Deref for ArcStr

type Target = str

The resulting type after dereferencing.

fn deref(&self) -> &str

Dereferences the value.

impl<'de> Deserialize<'de> for ArcStr

fn deserialize<D>(d: D) -> Result<ArcStr, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for ArcStr

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Drop for ArcStr

fn drop(&mut self)

Executes the destructor for this type.

impl From<&ArcStr> for ArcStr

fn from(s: &ArcStr) -> ArcStr

Converts to this type from the input type.

impl From<&String> for ArcStr

fn from(s: &String) -> ArcStr

Converts to this type from the input type.

impl From<&mut str> for ArcStr

fn from(s: &mut str) -> ArcStr

Converts to this type from the input type.

impl From<&str> for ArcStr

fn from(s: &str) -> ArcStr

Converts to this type from the input type.

impl From<Arc<str>> for ArcStr

fn from(s: Arc<str>) -> ArcStr

Converts to this type from the input type.

impl From<ArcStr> for Box<str>

fn from(s: ArcStr) -> Box<str>

Converts to this type from the input type.

impl From<Box<str>> for ArcStr

fn from(s: Box<str>) -> ArcStr

Converts to this type from the input type.

impl<'a> From<Cow<'a, str>> for ArcStr

fn from(s: Cow<'a, str>) -> ArcStr

Converts to this type from the input type.

impl From<Rc<str>> for ArcStr

fn from(s: Rc<str>) -> ArcStr

Converts to this type from the input type.

impl From<String> for ArcStr

fn from(v: String) -> ArcStr

Converts to this type from the input type.

impl<__S> FromInputValue<__S> for ArcStr

where __S: ScalarValue,

type Error = FieldError<__S>

Type of this conversion error.

fn from_input_value(input: &InputValue<__S>) -> Result<Self, Self::Error>

Performs the conversion.

fn from_implicit_null() -> Result<Self, Self::Error>

Performs the conversion from an absent value (e.g. to distinguish between implicit and explicit null).

impl<'___a, __S> FromScalarValue<'___a, __S> for ArcStr

where __S: ScalarValue, Self: '___a,

type Error = FieldError<__S>

Parsing error of a ScalarValue.

fn from_scalar_value(input: &'___a __S) -> Result<Self, Self::Error>

Parses the provided ScalarValue.

impl FromStr for ArcStr

type Err = Infallible

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<ArcStr, <ArcStr as FromStr>::Err>

Parses a string s to return a value of this type.

impl<__S> GraphQLType<__S> for ArcStr

where __S: ScalarValue,

fn name(_: &Self::TypeInfo) -> Option<ArcStr>

Returns name of this GraphQLType to expose.

fn meta(info: &Self::TypeInfo, registry: &mut Registry<__S>) -> MetaType<__S>

Returns MetaType representing this GraphQLType.

impl<__S> GraphQLValue<__S> for ArcStr

where __S: ScalarValue, Self: ToScalarValue<__S>,

type Context = ()

Context type for this GraphQLValue.

type TypeInfo = ()

Type that may carry additional schema information for this GraphQLValue.

fn type_name(&self, info: &Self::TypeInfo) -> Option<ArcStr>

Returns name of the GraphQLType exposed by this GraphQLValue.

fn resolve( &self, info: &(), selection: Option<&[Selection<'_, __S>]>, executor: &Executor<'_, '_, Self::Context, __S>, ) -> ExecutionResult<__S>

Resolves the provided selection_set against this GraphQLValue.

fn resolve_field( &self, _info: &Self::TypeInfo, _field_name: &str, _arguments: &Arguments<'_, S>, _executor: &Executor<'_, '_, Self::Context, S>, ) -> ExecutionResult<S>

Resolves the value of a single field on this GraphQLValue.

fn resolve_into_type( &self, info: &Self::TypeInfo, type_name: &str, selection_set: Option<&[Selection<'_, S>]>, executor: &Executor<'_, '_, Self::Context, S>, ) -> ExecutionResult<S>

Resolves this GraphQLValue (being an interface or an union) into a concrete downstream object type.

fn concrete_type_name( &self, context: &Self::Context, info: &Self::TypeInfo, ) -> String

Returns the concrete GraphQLType name for this GraphQLValue being an interface, an union or an object.

impl<__S> GraphQLValueAsync<__S> for ArcStr

where __S: ScalarValue + Send + Sync, Self: Sync,

fn resolve_async<'b>( &'b self, info: &'b Self::TypeInfo, selection_set: Option<&'b [Selection<'_, __S>]>, executor: &'b Executor<'_, '_, Self::Context, __S>, ) -> BoxFuture<'b, ExecutionResult<__S>>

Resolves the provided selection_set against this GraphQLValueAsync.

fn resolve_field_async<'a>( &'a self, _info: &'a Self::TypeInfo, _field_name: &'a str, _arguments: &'a Arguments<'_, S>, _executor: &'a Executor<'_, '_, Self::Context, S>, ) -> BoxFuture<'a, ExecutionResult<S>>

Resolves the value of a single field on this GraphQLValueAsync.

fn resolve_into_type_async<'a>( &'a self, info: &'a Self::TypeInfo, type_name: &str, selection_set: Option<&'a [Selection<'a, S>]>, executor: &'a Executor<'a, 'a, Self::Context, S>, ) -> BoxFuture<'a, ExecutionResult<S>>

Resolves this GraphQLValueAsync (being an interface or an union) into a concrete downstream object type.

impl Hash for ArcStr

fn hash<H>(&self, h: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Index<Range<usize>> for ArcStr

type Output = str

The returned type after indexing.

fn index(&self, i: Range<usize>) -> &<ArcStr as Index<Range<usize>>>::Output

Performs the indexing (container[index]) operation.

impl Index<RangeFrom<usize>> for ArcStr

type Output = str

The returned type after indexing.

fn index( &self, i: RangeFrom<usize>, ) -> &<ArcStr as Index<RangeFrom<usize>>>::Output

Performs the indexing (container[index]) operation.

impl Index<RangeFull> for ArcStr

type Output = str

The returned type after indexing.

fn index(&self, i: RangeFull) -> &<ArcStr as Index<RangeFull>>::Output

Performs the indexing (container[index]) operation.

impl Index<RangeInclusive<usize>> for ArcStr

type Output = str

The returned type after indexing.

fn index( &self, i: RangeInclusive<usize>, ) -> &<ArcStr as Index<RangeInclusive<usize>>>::Output

Performs the indexing (container[index]) operation.

impl Index<RangeTo<usize>> for ArcStr

type Output = str

The returned type after indexing.

fn index(&self, i: RangeTo<usize>) -> &<ArcStr as Index<RangeTo<usize>>>::Output

Performs the indexing (container[index]) operation.

impl Index<RangeToInclusive<usize>> for ArcStr

type Output = str

The returned type after indexing.

fn index( &self, i: RangeToInclusive<usize>, ) -> &<ArcStr as Index<RangeToInclusive<usize>>>::Output

Performs the indexing (container[index]) operation.

impl<S: ScalarValue> IntoInputValue<S> for ArcStr

where ArcStr: ToScalarValue<S>,

fn into_input_value(self) -> InputValue<S>

Converts this value into an InputValue.

impl<S: ScalarValue> IntoValue<S> for ArcStr

where ArcStr: ToScalarValue<S>,

fn into_value(self) -> Value<S>

Converts this value into a Value.

impl<__S> IsInputType<__S> for ArcStr

where __S: ScalarValue,

fn mark()

An arbitrary function without meaning.

impl<__S> IsOutputType<__S> for ArcStr

where __S: ScalarValue,

fn mark()

An arbitrary function without meaning.

impl Ord for ArcStr

fn cmp(&self, s: &ArcStr) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<__S> ParseScalarValue<__S> for ArcStr

where __S: ScalarValue,

fn from_str(token: ScalarToken<'_>) -> ParseScalarResult<__S>

See the trait documentation

impl<'a> PartialEq<&'a str> for ArcStr

fn eq(&self, s: &&'a str) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &&'a str) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<Arc<String>> for ArcStr

fn eq(&self, s: &Arc<String>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &Arc<String>) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<Arc<str>> for ArcStr

fn eq(&self, s: &Arc<str>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &Arc<str>) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<ArcStr> for &'a str

fn eq(&self, s: &ArcStr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &ArcStr) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<ArcStr> for Box<str>

fn eq(&self, s: &ArcStr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &ArcStr) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<ArcStr> for String

fn eq(&self, s: &ArcStr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &ArcStr) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<ArcStr> for str

fn eq(&self, s: &ArcStr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &ArcStr) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<Box<str>> for ArcStr

fn eq(&self, s: &Box<str>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &Box<str>) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<Cow<'a, str>> for ArcStr

fn eq(&self, s: &Cow<'a, str>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &Cow<'a, str>) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<Rc<String>> for ArcStr

fn eq(&self, s: &Rc<String>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &Rc<String>) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<Rc<str>> for ArcStr

fn eq(&self, s: &Rc<str>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &Rc<str>) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<String> for ArcStr

fn eq(&self, s: &String) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &String) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq<Substr> for ArcStr

fn eq(&self, o: &Substr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, o: &Substr) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'a> PartialEq<str> for ArcStr

fn eq(&self, s: &str) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, s: &str) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq for ArcStr

fn eq(&self, o: &ArcStr) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, o: &ArcStr) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for ArcStr

fn partial_cmp(&self, s: &ArcStr) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for ArcStr

fn serialize<S>( &self, ser: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<__S> ToInputValue<__S> for ArcStr

where __S: ScalarValue, Self: ToScalarValue<__S>,

fn to_input_value(&self) -> InputValue<__S>

Performs the conversion.

impl<__S> ToScalarValue<__S> for ArcStr

where __S: ScalarValue,

fn to_scalar_value(&self) -> __S

Converts this value into a ScalarValue.

impl Eq for ArcStr

impl Send for ArcStr

impl Sync for ArcStr