Enum ockam_core::lib::Result 1.0.0[−][src]
#[must_use = "this `Result` may be an `Err` variant, which should be handled"] pub enum Result<T, E> { Ok(T), Err(E), }
Expand description
Result
is a type that represents either success (Ok
) or failure (Err
).
See the module documentation for details.
Variants
Contains the success value
Contains the error value
Implementations
impl<T, E> Result<T, E>
[src]
impl<T, E> Result<T, E>
[src]#[must_use = "if you intended to assert that this is ok, consider `.unwrap()` instead"]pub const fn is_ok(&self) -> bool
1.0.0 (const: 1.48.0)[src]
#[must_use = "if you intended to assert that this is ok, consider `.unwrap()` instead"]pub const fn is_ok(&self) -> bool
1.0.0 (const: 1.48.0)[src]#[must_use = "if you intended to assert that this is err, consider `.unwrap_err()` instead"]pub const fn is_err(&self) -> bool
1.0.0 (const: 1.48.0)[src]
#[must_use = "if you intended to assert that this is err, consider `.unwrap_err()` instead"]pub const fn is_err(&self) -> bool
1.0.0 (const: 1.48.0)[src]#[must_use]pub fn contains<U>(&self, x: &U) -> bool where
U: PartialEq<T>,
[src]
🔬 This is a nightly-only experimental API. (option_result_contains
)
#[must_use]pub fn contains<U>(&self, x: &U) -> bool where
U: PartialEq<T>,
[src]option_result_contains
)Returns true
if the result is an Ok
value containing the given value.
Examples
#![feature(option_result_contains)] let x: Result<u32, &str> = Ok(2); assert_eq!(x.contains(&2), true); let x: Result<u32, &str> = Ok(3); assert_eq!(x.contains(&2), false); let x: Result<u32, &str> = Err("Some error message"); assert_eq!(x.contains(&2), false);
#[must_use]pub fn contains_err<F>(&self, f: &F) -> bool where
F: PartialEq<E>,
[src]
🔬 This is a nightly-only experimental API. (result_contains_err
)
#[must_use]pub fn contains_err<F>(&self, f: &F) -> bool where
F: PartialEq<E>,
[src]result_contains_err
)Returns true
if the result is an Err
value containing the given value.
Examples
#![feature(result_contains_err)] let x: Result<u32, &str> = Ok(2); assert_eq!(x.contains_err(&"Some error message"), false); let x: Result<u32, &str> = Err("Some error message"); assert_eq!(x.contains_err(&"Some error message"), true); let x: Result<u32, &str> = Err("Some other error message"); assert_eq!(x.contains_err(&"Some error message"), false);
pub fn err(self) -> Option<E>
[src]
pub fn err(self) -> Option<E>
[src]Converts from Result<T, E>
to Option<E>
.
Converts self
into an Option<E>
, consuming self
,
and discarding the success value, if any.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.err(), None); let x: Result<u32, &str> = Err("Nothing here"); assert_eq!(x.err(), Some("Nothing here"));
pub const fn as_ref(&self) -> Result<&T, &E>
1.0.0 (const: 1.48.0)[src]
pub const fn as_ref(&self) -> Result<&T, &E>
1.0.0 (const: 1.48.0)[src]Converts from &Result<T, E>
to Result<&T, &E>
.
Produces a new Result
, containing a reference
into the original, leaving the original in place.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.as_ref(), Ok(&2)); let x: Result<u32, &str> = Err("Error"); assert_eq!(x.as_ref(), Err(&"Error"));
pub fn as_mut(&mut self) -> Result<&mut T, &mut E>
[src]
pub fn as_mut(&mut self) -> Result<&mut T, &mut E>
[src]Converts from &mut Result<T, E>
to Result<&mut T, &mut E>
.
Examples
Basic usage:
fn mutate(r: &mut Result<i32, i32>) { match r.as_mut() { Ok(v) => *v = 42, Err(e) => *e = 0, } } let mut x: Result<i32, i32> = Ok(2); mutate(&mut x); assert_eq!(x.unwrap(), 42); let mut x: Result<i32, i32> = Err(13); mutate(&mut x); assert_eq!(x.unwrap_err(), 0);
pub fn map<U, F>(self, op: F) -> Result<U, E> where
F: FnOnce(T) -> U,
[src]
pub fn map<U, F>(self, op: F) -> Result<U, E> where
F: FnOnce(T) -> U,
[src]Maps a Result<T, E>
to Result<U, E>
by applying a function to a
contained Ok
value, leaving an Err
value untouched.
This function can be used to compose the results of two functions.
Examples
Print the numbers on each line of a string multiplied by two.
let line = "1\n2\n3\n4\n"; for num in line.lines() { match num.parse::<i32>().map(|i| i * 2) { Ok(n) => println!("{}", n), Err(..) => {} } }
pub fn map_or<U, F>(self, default: U, f: F) -> U where
F: FnOnce(T) -> U,
1.41.0[src]
pub fn map_or<U, F>(self, default: U, f: F) -> U where
F: FnOnce(T) -> U,
1.41.0[src]Returns the provided default (if Err
), or
applies a function to the contained value (if Ok
),
Arguments passed to map_or
are eagerly evaluated; if you are passing
the result of a function call, it is recommended to use map_or_else
,
which is lazily evaluated.
Examples
let x: Result<_, &str> = Ok("foo"); assert_eq!(x.map_or(42, |v| v.len()), 3); let x: Result<&str, _> = Err("bar"); assert_eq!(x.map_or(42, |v| v.len()), 42);
pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U where
F: FnOnce(T) -> U,
D: FnOnce(E) -> U,
1.41.0[src]
pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U where
F: FnOnce(T) -> U,
D: FnOnce(E) -> U,
1.41.0[src]Maps a Result<T, E>
to U
by applying a fallback function to a
contained Err
value, or a default function to a
contained Ok
value.
This function can be used to unpack a successful result while handling an error.
Examples
Basic usage:
let k = 21; let x : Result<_, &str> = Ok("foo"); assert_eq!(x.map_or_else(|e| k * 2, |v| v.len()), 3); let x : Result<&str, _> = Err("bar"); assert_eq!(x.map_or_else(|e| k * 2, |v| v.len()), 42);
pub fn map_err<F, O>(self, op: O) -> Result<T, F> where
O: FnOnce(E) -> F,
[src]
pub fn map_err<F, O>(self, op: O) -> Result<T, F> where
O: FnOnce(E) -> F,
[src]Maps a Result<T, E>
to Result<T, F>
by applying a function to a
contained Err
value, leaving an Ok
value untouched.
This function can be used to pass through a successful result while handling an error.
Examples
Basic usage:
fn stringify(x: u32) -> String { format!("error code: {}", x) } let x: Result<u32, u32> = Ok(2); assert_eq!(x.map_err(stringify), Ok(2)); let x: Result<u32, u32> = Err(13); assert_eq!(x.map_err(stringify), Err("error code: 13".to_string()));
pub fn iter(&self) -> Iter<'_, T>ⓘ
[src]
pub fn iter(&self) -> Iter<'_, T>ⓘ
[src]Returns an iterator over the possibly contained value.
The iterator yields one value if the result is Result::Ok
, otherwise none.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(7); assert_eq!(x.iter().next(), Some(&7)); let x: Result<u32, &str> = Err("nothing!"); assert_eq!(x.iter().next(), None);
pub fn iter_mut(&mut self) -> IterMut<'_, T>ⓘ
[src]
pub fn iter_mut(&mut self) -> IterMut<'_, T>ⓘ
[src]Returns a mutable iterator over the possibly contained value.
The iterator yields one value if the result is Result::Ok
, otherwise none.
Examples
Basic usage:
let mut x: Result<u32, &str> = Ok(7); match x.iter_mut().next() { Some(v) => *v = 40, None => {}, } assert_eq!(x, Ok(40)); let mut x: Result<u32, &str> = Err("nothing!"); assert_eq!(x.iter_mut().next(), None);
pub fn and<U>(self, res: Result<U, E>) -> Result<U, E>
[src]
pub fn and<U>(self, res: Result<U, E>) -> Result<U, E>
[src]Returns res
if the result is Ok
, otherwise returns the Err
value of self
.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); let y: Result<&str, &str> = Err("late error"); assert_eq!(x.and(y), Err("late error")); let x: Result<u32, &str> = Err("early error"); let y: Result<&str, &str> = Ok("foo"); assert_eq!(x.and(y), Err("early error")); let x: Result<u32, &str> = Err("not a 2"); let y: Result<&str, &str> = Err("late error"); assert_eq!(x.and(y), Err("not a 2")); let x: Result<u32, &str> = Ok(2); let y: Result<&str, &str> = Ok("different result type"); assert_eq!(x.and(y), Ok("different result type"));
pub fn and_then<U, F>(self, op: F) -> Result<U, E> where
F: FnOnce(T) -> Result<U, E>,
[src]
pub fn and_then<U, F>(self, op: F) -> Result<U, E> where
F: FnOnce(T) -> Result<U, E>,
[src]Calls op
if the result is Ok
, otherwise returns the Err
value of self
.
This function can be used for control flow based on Result
values.
Examples
Basic usage:
fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) } fn err(x: u32) -> Result<u32, u32> { Err(x) } assert_eq!(Ok(2).and_then(sq).and_then(sq), Ok(16)); assert_eq!(Ok(2).and_then(sq).and_then(err), Err(4)); assert_eq!(Ok(2).and_then(err).and_then(sq), Err(2)); assert_eq!(Err(3).and_then(sq).and_then(sq), Err(3));
pub fn or<F>(self, res: Result<T, F>) -> Result<T, F>
[src]
pub fn or<F>(self, res: Result<T, F>) -> Result<T, F>
[src]Returns res
if the result is Err
, otherwise returns the Ok
value of self
.
Arguments passed to or
are eagerly evaluated; if you are passing the
result of a function call, it is recommended to use or_else
, which is
lazily evaluated.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); let y: Result<u32, &str> = Err("late error"); assert_eq!(x.or(y), Ok(2)); let x: Result<u32, &str> = Err("early error"); let y: Result<u32, &str> = Ok(2); assert_eq!(x.or(y), Ok(2)); let x: Result<u32, &str> = Err("not a 2"); let y: Result<u32, &str> = Err("late error"); assert_eq!(x.or(y), Err("late error")); let x: Result<u32, &str> = Ok(2); let y: Result<u32, &str> = Ok(100); assert_eq!(x.or(y), Ok(2));
pub fn or_else<F, O>(self, op: O) -> Result<T, F> where
O: FnOnce(E) -> Result<T, F>,
[src]
pub fn or_else<F, O>(self, op: O) -> Result<T, F> where
O: FnOnce(E) -> Result<T, F>,
[src]Calls op
if the result is Err
, otherwise returns the Ok
value of self
.
This function can be used for control flow based on result values.
Examples
Basic usage:
fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) } fn err(x: u32) -> Result<u32, u32> { Err(x) } assert_eq!(Ok(2).or_else(sq).or_else(sq), Ok(2)); assert_eq!(Ok(2).or_else(err).or_else(sq), Ok(2)); assert_eq!(Err(3).or_else(sq).or_else(err), Ok(9)); assert_eq!(Err(3).or_else(err).or_else(err), Err(3));
pub fn unwrap_or(self, default: T) -> T
[src]
pub fn unwrap_or(self, default: T) -> T
[src]Returns the contained Ok
value or a provided default.
Arguments passed to unwrap_or
are eagerly evaluated; if you are passing
the result of a function call, it is recommended to use unwrap_or_else
,
which is lazily evaluated.
Examples
Basic usage:
let default = 2; let x: Result<u32, &str> = Ok(9); assert_eq!(x.unwrap_or(default), 9); let x: Result<u32, &str> = Err("error"); assert_eq!(x.unwrap_or(default), default);
pub fn unwrap_or_else<F>(self, op: F) -> T where
F: FnOnce(E) -> T,
[src]
pub fn unwrap_or_else<F>(self, op: F) -> T where
F: FnOnce(E) -> T,
[src]pub unsafe fn unwrap_unchecked(self) -> T
[src]
🔬 This is a nightly-only experimental API. (option_result_unwrap_unchecked
)
newly added
pub unsafe fn unwrap_unchecked(self) -> T
[src]🔬 This is a nightly-only experimental API. (option_result_unwrap_unchecked
)
newly added
Returns the contained Ok
value, consuming the self
value,
without checking that the value is not an Err
.
Safety
Calling this method on an Err
is undefined behavior.
Examples
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Ok(2); assert_eq!(unsafe { x.unwrap_unchecked() }, 2);
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Err("emergency failure"); unsafe { x.unwrap_unchecked(); } // Undefined behavior!
pub unsafe fn unwrap_err_unchecked(self) -> E
[src]
🔬 This is a nightly-only experimental API. (option_result_unwrap_unchecked
)
newly added
pub unsafe fn unwrap_err_unchecked(self) -> E
[src]🔬 This is a nightly-only experimental API. (option_result_unwrap_unchecked
)
newly added
Returns the contained Err
value, consuming the self
value,
without checking that the value is not an Ok
.
Safety
Calling this method on an Ok
is undefined behavior.
Examples
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Ok(2); unsafe { x.unwrap_err_unchecked() }; // Undefined behavior!
#![feature(option_result_unwrap_unchecked)] let x: Result<u32, &str> = Err("emergency failure"); assert_eq!(unsafe { x.unwrap_err_unchecked() }, "emergency failure");
impl<'_, T, E> Result<&'_ T, E> where
T: Copy,
[src]
impl<'_, T, E> Result<&'_ T, E> where
T: Copy,
[src]pub fn copied(self) -> Result<T, E>
[src]
🔬 This is a nightly-only experimental API. (result_copied
)
newly added
pub fn copied(self) -> Result<T, E>
[src]🔬 This is a nightly-only experimental API. (result_copied
)
newly added
Maps a Result<&T, E>
to a Result<T, E>
by copying the contents of the
Ok
part.
Examples
#![feature(result_copied)] let val = 12; let x: Result<&i32, i32> = Ok(&val); assert_eq!(x, Ok(&12)); let copied = x.copied(); assert_eq!(copied, Ok(12));
impl<'_, T, E> Result<&'_ mut T, E> where
T: Copy,
[src]
impl<'_, T, E> Result<&'_ mut T, E> where
T: Copy,
[src]pub fn copied(self) -> Result<T, E>
[src]
🔬 This is a nightly-only experimental API. (result_copied
)
newly added
pub fn copied(self) -> Result<T, E>
[src]🔬 This is a nightly-only experimental API. (result_copied
)
newly added
Maps a Result<&mut T, E>
to a Result<T, E>
by copying the contents of the
Ok
part.
Examples
#![feature(result_copied)] let mut val = 12; let x: Result<&mut i32, i32> = Ok(&mut val); assert_eq!(x, Ok(&mut 12)); let copied = x.copied(); assert_eq!(copied, Ok(12));
impl<'_, T, E> Result<&'_ T, E> where
T: Clone,
[src]
impl<'_, T, E> Result<&'_ T, E> where
T: Clone,
[src]pub fn cloned(self) -> Result<T, E>
[src]
🔬 This is a nightly-only experimental API. (result_cloned
)
newly added
pub fn cloned(self) -> Result<T, E>
[src]🔬 This is a nightly-only experimental API. (result_cloned
)
newly added
Maps a Result<&T, E>
to a Result<T, E>
by cloning the contents of the
Ok
part.
Examples
#![feature(result_cloned)] let val = 12; let x: Result<&i32, i32> = Ok(&val); assert_eq!(x, Ok(&12)); let cloned = x.cloned(); assert_eq!(cloned, Ok(12));
impl<'_, T, E> Result<&'_ mut T, E> where
T: Clone,
[src]
impl<'_, T, E> Result<&'_ mut T, E> where
T: Clone,
[src]pub fn cloned(self) -> Result<T, E>
[src]
🔬 This is a nightly-only experimental API. (result_cloned
)
newly added
pub fn cloned(self) -> Result<T, E>
[src]🔬 This is a nightly-only experimental API. (result_cloned
)
newly added
Maps a Result<&mut T, E>
to a Result<T, E>
by cloning the contents of the
Ok
part.
Examples
#![feature(result_cloned)] let mut val = 12; let x: Result<&mut i32, i32> = Ok(&mut val); assert_eq!(x, Ok(&mut 12)); let cloned = x.cloned(); assert_eq!(cloned, Ok(12));
impl<T, E> Result<T, E> where
E: Debug,
[src]
impl<T, E> Result<T, E> where
E: Debug,
[src]pub fn expect(self, msg: &str) -> T
1.4.0[src]
pub fn expect(self, msg: &str) -> T
1.4.0[src]Returns the contained Ok
value, consuming the self
value.
Panics
Panics if the value is an Err
, with a panic message including the
passed message, and the content of the Err
.
Examples
Basic usage:
let x: Result<u32, &str> = Err("emergency failure"); x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
pub fn unwrap(self) -> T
[src]
pub fn unwrap(self) -> T
[src]Returns the contained Ok
value, consuming the self
value.
Because this function may panic, its use is generally discouraged.
Instead, prefer to use pattern matching and handle the Err
case explicitly, or call unwrap_or
, unwrap_or_else
, or
unwrap_or_default
.
Panics
Panics if the value is an Err
, with a panic message provided by the
Err
’s value.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(2); assert_eq!(x.unwrap(), 2);
let x: Result<u32, &str> = Err("emergency failure"); x.unwrap(); // panics with `emergency failure`
impl<T, E> Result<T, E> where
T: Debug,
[src]
impl<T, E> Result<T, E> where
T: Debug,
[src]pub fn expect_err(self, msg: &str) -> E
1.17.0[src]
pub fn expect_err(self, msg: &str) -> E
1.17.0[src]Returns the contained Err
value, consuming the self
value.
Panics
Panics if the value is an Ok
, with a panic message including the
passed message, and the content of the Ok
.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(10); x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
pub fn unwrap_err(self) -> E
[src]
pub fn unwrap_err(self) -> E
[src]Returns the contained Err
value, consuming the self
value.
Panics
Panics if the value is an Ok
, with a custom panic message provided
by the Ok
’s value.
Examples
let x: Result<u32, &str> = Ok(2); x.unwrap_err(); // panics with `2`
let x: Result<u32, &str> = Err("emergency failure"); assert_eq!(x.unwrap_err(), "emergency failure");
impl<T, E> Result<T, E> where
T: Default,
[src]
impl<T, E> Result<T, E> where
T: Default,
[src]pub fn unwrap_or_default(self) -> T
1.16.0[src]
pub fn unwrap_or_default(self) -> T
1.16.0[src]Returns the contained Ok
value or a default
Consumes the self
argument then, if Ok
, returns the contained
value, otherwise if Err
, returns the default value for that
type.
Examples
Converts a string to an integer, turning poorly-formed strings
into 0 (the default value for integers). parse
converts
a string to any other type that implements FromStr
, returning an
Err
on error.
let good_year_from_input = "1909"; let bad_year_from_input = "190blarg"; let good_year = good_year_from_input.parse().unwrap_or_default(); let bad_year = bad_year_from_input.parse().unwrap_or_default(); assert_eq!(1909, good_year); assert_eq!(0, bad_year);
impl<T, E> Result<T, E> where
E: Into<!>,
[src]
impl<T, E> Result<T, E> where
E: Into<!>,
[src]pub fn into_ok(self) -> T
[src]
🔬 This is a nightly-only experimental API. (unwrap_infallible
)
newly added
pub fn into_ok(self) -> T
[src]🔬 This is a nightly-only experimental API. (unwrap_infallible
)
newly added
Returns the contained Ok
value, but never panics.
Unlike unwrap
, this method is known to never panic on the
result types it is implemented for. Therefore, it can be used
instead of unwrap
as a maintainability safeguard that will fail
to compile if the error type of the Result
is later changed
to an error that can actually occur.
Examples
Basic usage:
fn only_good_news() -> Result<String, !> { Ok("this is fine".into()) } let s: String = only_good_news().into_ok(); println!("{}", s);
impl<T, E> Result<T, E> where
T: Into<!>,
[src]
impl<T, E> Result<T, E> where
T: Into<!>,
[src]pub fn into_err(self) -> E
[src]
🔬 This is a nightly-only experimental API. (unwrap_infallible
)
newly added
pub fn into_err(self) -> E
[src]🔬 This is a nightly-only experimental API. (unwrap_infallible
)
newly added
Returns the contained Err
value, but never panics.
Unlike unwrap_err
, this method is known to never panic on the
result types it is implemented for. Therefore, it can be used
instead of unwrap_err
as a maintainability safeguard that will fail
to compile if the ok type of the Result
is later changed
to a type that can actually occur.
Examples
Basic usage:
fn only_bad_news() -> Result<!, String> { Err("Oops, it failed".into()) } let error: String = only_bad_news().into_err(); println!("{}", error);
impl<T, E> Result<T, E> where
T: Deref,
[src]
impl<T, E> Result<T, E> where
T: Deref,
[src]pub fn as_deref(&self) -> Result<&<T as Deref>::Target, &E>
1.47.0[src]
pub fn as_deref(&self) -> Result<&<T as Deref>::Target, &E>
1.47.0[src]Converts from Result<T, E>
(or &Result<T, E>
) to Result<&<T as Deref>::Target, &E>
.
Coerces the Ok
variant of the original Result
via Deref
and returns the new Result
.
Examples
let x: Result<String, u32> = Ok("hello".to_string()); let y: Result<&str, &u32> = Ok("hello"); assert_eq!(x.as_deref(), y); let x: Result<String, u32> = Err(42); let y: Result<&str, &u32> = Err(&42); assert_eq!(x.as_deref(), y);
impl<T, E> Result<T, E> where
T: DerefMut,
[src]
impl<T, E> Result<T, E> where
T: DerefMut,
[src]pub fn as_deref_mut(&mut self) -> Result<&mut <T as Deref>::Target, &mut E>
1.47.0[src]
pub fn as_deref_mut(&mut self) -> Result<&mut <T as Deref>::Target, &mut E>
1.47.0[src]Converts from Result<T, E>
(or &mut Result<T, E>
) to Result<&mut <T as DerefMut>::Target, &mut E>
.
Coerces the Ok
variant of the original Result
via DerefMut
and returns the new Result
.
Examples
let mut s = "HELLO".to_string(); let mut x: Result<String, u32> = Ok("hello".to_string()); let y: Result<&mut str, &mut u32> = Ok(&mut s); assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y); let mut i = 42; let mut x: Result<String, u32> = Err(42); let y: Result<&mut str, &mut u32> = Err(&mut i); assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
impl<T, E> Result<Option<T>, E>
[src]
impl<T, E> Result<Option<T>, E>
[src]pub const fn transpose(self) -> Option<Result<T, E>>
1.33.0[src]
pub const fn transpose(self) -> Option<Result<T, E>>
1.33.0[src]Transposes a Result
of an Option
into an Option
of a Result
.
Ok(None)
will be mapped to None
.
Ok(Some(_))
and Err(_)
will be mapped to Some(Ok(_))
and Some(Err(_))
.
Examples
#[derive(Debug, Eq, PartialEq)] struct SomeErr; let x: Result<Option<i32>, SomeErr> = Ok(Some(5)); let y: Option<Result<i32, SomeErr>> = Some(Ok(5)); assert_eq!(x.transpose(), y);
impl<T, E> Result<Result<T, E>, E>
[src]
impl<T, E> Result<Result<T, E>, E>
[src]pub fn flatten(self) -> Result<T, E>
[src]
🔬 This is a nightly-only experimental API. (result_flattening
)
pub fn flatten(self) -> Result<T, E>
[src]result_flattening
)Converts from Result<Result<T, E>, E>
to Result<T, E>
Examples
Basic usage:
#![feature(result_flattening)] let x: Result<Result<&'static str, u32>, u32> = Ok(Ok("hello")); assert_eq!(Ok("hello"), x.flatten()); let x: Result<Result<&'static str, u32>, u32> = Ok(Err(6)); assert_eq!(Err(6), x.flatten()); let x: Result<Result<&'static str, u32>, u32> = Err(6); assert_eq!(Err(6), x.flatten());
Flattening only removes one level of nesting at a time:
#![feature(result_flattening)] let x: Result<Result<Result<&'static str, u32>, u32>, u32> = Ok(Ok(Ok("hello"))); assert_eq!(Ok(Ok("hello")), x.flatten()); assert_eq!(Ok("hello"), x.flatten().flatten());
impl<T> Result<T, T>
[src]
impl<T> Result<T, T>
[src]pub const fn into_ok_or_err(self) -> T
[src]
🔬 This is a nightly-only experimental API. (result_into_ok_or_err
)
newly added
pub const fn into_ok_or_err(self) -> T
[src]🔬 This is a nightly-only experimental API. (result_into_ok_or_err
)
newly added
Returns the Ok
value if self
is Ok
, and the Err
value if
self
is Err
.
In other words, this function returns the value (the T
) of a
Result<T, T>
, regardless of whether or not that result is Ok
or
Err
.
This can be useful in conjunction with APIs such as
Atomic*::compare_exchange
, or slice::binary_search
, but only in
cases where you don’t care if the result was Ok
or not.
Examples
#![feature(result_into_ok_or_err)] let ok: Result<u32, u32> = Ok(3); let err: Result<u32, u32> = Err(4); assert_eq!(ok.into_ok_or_err(), 3); assert_eq!(err.into_ok_or_err(), 4);
Trait Implementations
impl<'de, T, E> Deserialize<'de> for Result<T, E> where
T: Deserialize<'de>,
E: Deserialize<'de>,
[src]
impl<'de, T, E> Deserialize<'de> for Result<T, E> where
T: Deserialize<'de>,
E: Deserialize<'de>,
[src]pub fn deserialize<D>(
deserializer: D
) -> Result<Result<T, E>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
[src]
pub fn deserialize<D>(
deserializer: D
) -> Result<Result<T, E>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
[src]Deserialize this value from the given Serde deserializer. Read more
impl<A, E, V> FromIterator<Result<A, E>> for Result<V, E> where
V: FromIterator<A>,
[src]
impl<A, E, V> FromIterator<Result<A, E>> for Result<V, E> where
V: FromIterator<A>,
[src]pub fn from_iter<I>(iter: I) -> Result<V, E> where
I: IntoIterator<Item = Result<A, E>>,
[src]
pub fn from_iter<I>(iter: I) -> Result<V, E> where
I: IntoIterator<Item = Result<A, E>>,
[src]Takes each element in the Iterator
: if it is an Err
, no further
elements are taken, and the Err
is returned. Should no Err
occur, a
container with the values of each Result
is returned.
Here is an example which increments every integer in a vector, checking for overflow:
let v = vec![1, 2]; let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32| x.checked_add(1).ok_or("Overflow!") ).collect(); assert_eq!(res, Ok(vec![2, 3]));
Here is another example that tries to subtract one from another list of integers, this time checking for underflow:
let v = vec![1, 2, 0]; let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32| x.checked_sub(1).ok_or("Underflow!") ).collect(); assert_eq!(res, Err("Underflow!"));
Here is a variation on the previous example, showing that no
further elements are taken from iter
after the first Err
.
let v = vec![3, 2, 1, 10]; let mut shared = 0; let res: Result<Vec<u32>, &'static str> = v.iter().map(|x: &u32| { shared += x; x.checked_sub(2).ok_or("Underflow!") }).collect(); assert_eq!(res, Err("Underflow!")); assert_eq!(shared, 6);
Since the third element caused an underflow, no further elements were taken,
so the final value of shared
is 6 (= 3 + 2 + 1
), not 16.
impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Result<T, F>> where
F: From<E>,
[src]
impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Result<T, F>> where
F: From<E>,
[src]pub fn from_residual(x: Result<Infallible, E>) -> Poll<Result<T, F>>
[src]
pub fn from_residual(x: Result<Infallible, E>) -> Poll<Result<T, F>>
[src]try_trait_v2
)Constructs the type from a compatible Residual
type. Read more
impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Option<Result<T, F>>> where
F: From<E>,
[src]
impl<T, E, F> FromResidual<Result<Infallible, E>> for Poll<Option<Result<T, F>>> where
F: From<E>,
[src]pub fn from_residual(x: Result<Infallible, E>) -> Poll<Option<Result<T, F>>>
[src]
pub fn from_residual(x: Result<Infallible, E>) -> Poll<Option<Result<T, F>>>
[src]try_trait_v2
)Constructs the type from a compatible Residual
type. Read more
impl<T, E, F> FromResidual<Result<Infallible, E>> for Result<T, F> where
F: From<E>,
[src]
impl<T, E, F> FromResidual<Result<Infallible, E>> for Result<T, F> where
F: From<E>,
[src]pub fn from_residual(residual: Result<Infallible, E>) -> Result<T, F>
[src]
pub fn from_residual(residual: Result<Infallible, E>) -> Result<T, F>
[src]try_trait_v2
)Constructs the type from a compatible Residual
type. Read more
impl<'a, T, E> IntoIterator for &'a mut Result<T, E>
1.4.0[src]
impl<'a, T, E> IntoIterator for &'a mut Result<T, E>
1.4.0[src]impl<T, E> IntoIterator for Result<T, E>
[src]
impl<T, E> IntoIterator for Result<T, E>
[src]pub fn into_iter(self) -> IntoIter<T>ⓘ
[src]
pub fn into_iter(self) -> IntoIter<T>ⓘ
[src]Returns a consuming iterator over the possibly contained value.
The iterator yields one value if the result is Result::Ok
, otherwise none.
Examples
Basic usage:
let x: Result<u32, &str> = Ok(5); let v: Vec<u32> = x.into_iter().collect(); assert_eq!(v, [5]); let x: Result<u32, &str> = Err("nothing!"); let v: Vec<u32> = x.into_iter().collect(); assert_eq!(v, []);
impl<'a, T, E> IntoIterator for &'a Result<T, E>
1.4.0[src]
impl<'a, T, E> IntoIterator for &'a Result<T, E>
1.4.0[src]impl<T, E> Ord for Result<T, E> where
T: Ord,
E: Ord,
[src]
impl<T, E> Ord for Result<T, E> where
T: Ord,
E: Ord,
[src]impl<T, E> PartialOrd<Result<T, E>> for Result<T, E> where
T: PartialOrd<T>,
E: PartialOrd<E>,
[src]
impl<T, E> PartialOrd<Result<T, E>> for Result<T, E> where
T: PartialOrd<T>,
E: PartialOrd<E>,
[src]pub fn partial_cmp(&self, other: &Result<T, E>) -> Option<Ordering>
[src]
pub fn partial_cmp(&self, other: &Result<T, E>) -> Option<Ordering>
[src]This method returns an ordering between self
and other
values if one exists. Read more
#[must_use]fn lt(&self, other: &Rhs) -> bool
[src]
#[must_use]fn lt(&self, other: &Rhs) -> bool
[src]This method tests less than (for self
and other
) and is used by the <
operator. Read more
#[must_use]fn le(&self, other: &Rhs) -> bool
[src]
#[must_use]fn le(&self, other: &Rhs) -> bool
[src]This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
impl<T, E> Serialize for Result<T, E> where
T: Serialize,
E: Serialize,
[src]
impl<T, E> Serialize for Result<T, E> where
T: Serialize,
E: Serialize,
[src]pub fn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
[src]
pub fn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
[src]Serialize this value into the given Serde serializer. Read more
impl<T, U, E> Sum<Result<U, E>> for Result<T, E> where
T: Sum<U>,
1.16.0[src]
impl<T, U, E> Sum<Result<U, E>> for Result<T, E> where
T: Sum<U>,
1.16.0[src]pub fn sum<I>(iter: I) -> Result<T, E> where
I: Iterator<Item = Result<U, E>>,
[src]
pub fn sum<I>(iter: I) -> Result<T, E> where
I: Iterator<Item = Result<U, E>>,
[src]Takes each element in the Iterator
: if it is an Err
, no further
elements are taken, and the Err
is returned. Should no Err
occur, the sum of all elements is returned.
Examples
This sums up every integer in a vector, rejecting the sum if a negative element is encountered:
let v = vec![1, 2]; let res: Result<i32, &'static str> = v.iter().map(|&x: &i32| if x < 0 { Err("Negative element found") } else { Ok(x) } ).sum(); assert_eq!(res, Ok(3));
impl<E> Termination for Result<!, E> where
E: Debug,
[src]
impl<E> Termination for Result<!, E> where
E: Debug,
[src]impl<E> Termination for Result<(), E> where
E: Debug,
[src]
impl<E> Termination for Result<(), E> where
E: Debug,
[src]impl<T, E> Try for Result<T, E>
[src]
impl<T, E> Try for Result<T, E>
[src]type Output = T
type Output = T
try_trait_v2
)The type of the value produced by ?
when not short-circuiting.
type Residual = Result<Infallible, E>
type Residual = Result<Infallible, E>
try_trait_v2
)The type of the value passed to FromResidual::from_residual
as part of ?
when short-circuiting. Read more
pub fn from_output(output: <Result<T, E> as Try>::Output) -> Result<T, E>
[src]
pub fn from_output(output: <Result<T, E> as Try>::Output) -> Result<T, E>
[src]try_trait_v2
)Constructs the type from its Output
type. Read more
pub fn branch(
self
) -> ControlFlow<<Result<T, E> as Try>::Residual, <Result<T, E> as Try>::Output>
[src]
pub fn branch(
self
) -> ControlFlow<<Result<T, E> as Try>::Residual, <Result<T, E> as Try>::Output>
[src]try_trait_v2
)Used in ?
to decide whether the operator should produce a value
(because this returned ControlFlow::Continue
)
or propagate a value back to the caller
(because this returned ControlFlow::Break
). Read more
impl<T, E> Copy for Result<T, E> where
T: Copy,
E: Copy,
[src]
T: Copy,
E: Copy,
impl<T, E> Eq for Result<T, E> where
T: Eq,
E: Eq,
[src]
T: Eq,
E: Eq,
impl<T, E> StructuralEq for Result<T, E>
[src]
impl<T, E> StructuralPartialEq for Result<T, E>
[src]
Auto Trait Implementations
impl<T, E> RefUnwindSafe for Result<T, E> where
E: RefUnwindSafe,
T: RefUnwindSafe,
E: RefUnwindSafe,
T: RefUnwindSafe,
impl<T, E> Send for Result<T, E> where
E: Send,
T: Send,
E: Send,
T: Send,
impl<T, E> Sync for Result<T, E> where
E: Sync,
T: Sync,
E: Sync,
T: Sync,
impl<T, E> Unpin for Result<T, E> where
E: Unpin,
T: Unpin,
E: Unpin,
T: Unpin,
impl<T, E> UnwindSafe for Result<T, E> where
E: UnwindSafe,
T: UnwindSafe,
E: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]pub fn borrow_mut(&mut self) -> &mut T
[src]
pub fn borrow_mut(&mut self) -> &mut T
[src]Mutably borrows from an owned value. Read more
impl<T> ToOwned for T where
T: Clone,
[src]
impl<T> ToOwned for T where
T: Clone,
[src]type Owned = T
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
[src]
pub fn to_owned(&self) -> T
[src]Creates owned data from borrowed data, usually by cloning. Read more
pub fn clone_into(&self, target: &mut T)
[src]
pub fn clone_into(&self, target: &mut T)
[src]🔬 This is a nightly-only experimental API. (toowned_clone_into
)
recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
pub fn vzip(self) -> V
impl<T> DeserializeOwned for T where
T: for<'de> Deserialize<'de>,
[src]
T: for<'de> Deserialize<'de>,