Trait Extend

pub trait Extend<A> {
    // Required method
    fn extend<T>(&mut self, iter: T)
       where T: IntoIterator<Item = A>;

    // Provided methods
    fn extend_one(&mut self, item: A) { ... }
    fn extend_reserve(&mut self, additional: usize) { ... }
}

Extend a collection with the contents of an iterator.

Iterators produce a series of values, and collections can also be thought of as a series of values. The Extend trait bridges this gap, allowing you to extend a collection by including the contents of that iterator. When extending a collection with an already existing key, that entry is updated or, in the case of collections that permit multiple entries with equal keys, that entry is inserted.

Examples

Basic usage:

// You can extend a String with some chars:
let mut message = String::from("The first three letters are: ");

message.extend(&['a', 'b', 'c']);

assert_eq!("abc", &message[29..32]);

Implementing Extend:

// A sample collection, that's just a wrapper over Vec<T>
#[derive(Debug)]
struct MyCollection(Vec<i32>);

// Let's give it some methods so we can create one and add things
// to it.
impl MyCollection {
    fn new() -> MyCollection {
        MyCollection(Vec::new())
    }

    fn add(&mut self, elem: i32) {
        self.0.push(elem);
    }
}

// since MyCollection has a list of i32s, we implement Extend for i32
impl Extend<i32> for MyCollection {

    // This is a bit simpler with the concrete type signature: we can call
    // extend on anything which can be turned into an Iterator which gives
    // us i32s. Because we need i32s to put into MyCollection.
    fn extend<T: IntoIterator<Item=i32>>(&mut self, iter: T) {

        // The implementation is very straightforward: loop through the
        // iterator, and add() each element to ourselves.
        for elem in iter {
            self.add(elem);
        }
    }
}

let mut c = MyCollection::new();

c.add(5);
c.add(6);
c.add(7);

// let's extend our collection with three more numbers
c.extend(vec![1, 2, 3]);

// we've added these elements onto the end
assert_eq!("MyCollection([5, 6, 7, 1, 2, 3])", format!("{c:?}"));

Required Methods

fn extend<T>(&mut self, iter: T)

where T: IntoIterator<Item = A>,

Extends a collection with the contents of an iterator.

As this is the only required method for this trait, the trait-level docs contain more details.

Examples

// You can extend a String with some chars:
let mut message = String::from("abc");

message.extend(['d', 'e', 'f'].iter());

assert_eq!("abcdef", &message);

Provided Methods

fn extend_one(&mut self, item: A)

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

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

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

Reserves capacity in a collection for the given number of additional elements.

The default implementation does nothing.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl Extend<(String, Value)> for Map<String, Value>

impl Extend<AsciiChar> for String

impl Extend<char> for String

impl Extend<u8> for BytesMut

impl Extend<()> for ()

impl Extend<String> for String

impl Extend<OsString> for OsString

impl Extend<Bytes> for BytesMut

impl Extend<CipherCtxFlags> for CipherCtxFlags

impl Extend<CMSOptions> for CMSOptions

impl Extend<OcspFlag> for OcspFlag

impl Extend<Pkcs7Flags> for Pkcs7Flags

impl Extend<ExtensionContext> for ExtensionContext

impl Extend<ShutdownState> for ShutdownState

impl Extend<SslMode> for SslMode

impl Extend<SslOptions> for SslOptions

impl Extend<SslSessionCacheMode> for SslSessionCacheMode

impl Extend<SslVerifyMode> for SslVerifyMode

impl Extend<X509CheckFlags> for X509CheckFlags

impl Extend<X509VerifyFlags> for X509VerifyFlags

impl<'a> Extend<&'a AsciiChar> for String

impl<'a> Extend<&'a char> for String

impl<'a> Extend<&'a str> for String

impl<'a> Extend<&'a u8> for BytesMut

impl<'a> Extend<&'a OsStr> for OsString

impl<'a> Extend<Cow<'a, str>> for String

impl<'a> Extend<Cow<'a, OsStr>> for OsString

impl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>

where K: Ord + Copy, V: Copy, A: Allocator + Clone,

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for std::collections::hash::map::HashMap<K, V, S>

where K: Eq + Hash + Copy, V: Copy, S: BuildHasher,

impl<'a, K, V, S, A> Extend<&'a (K, V)> for hashbrown::map::HashMap<K, V, S, A>

where K: Eq + Hash + Copy, V: Copy, S: BuildHasher, A: Allocator,

Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.

impl<'a, K, V, S, A> Extend<(&'a K, &'a V)> for hashbrown::map::HashMap<K, V, S, A>

where K: Eq + Hash + Copy, V: Copy, S: BuildHasher, A: Allocator,

Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.

impl<'a, M, T1, T2, O1, O2> Extend<BitRef<'a, M, T2, O2>> for BitVec<T1, O1>

where M: Mutability, T1: BitStore, T2: BitStore, O1: BitOrder, O2: BitOrder,

Bit-Vector Extension by Proxy References

DO NOT use this. You clearly have a bit-slice. Use .extend_from_bitslice() instead!

Iterating over a bit-slice requires loading from memory and constructing a proxy reference for each bit. This is needlessly slow; the specialized method is able to avoid this per-bit cost and possibly even use batched operations.

impl<'a, T, A> Extend<&'a T> for BTreeSet<T, A>

where T: 'a + Ord + Copy, A: Allocator + Clone,

impl<'a, T, A> Extend<&'a T> for BinaryHeap<T, A>

where T: 'a + Ord + Copy, A: Allocator,

impl<'a, T, A> Extend<&'a T> for LinkedList<T, A>

where T: 'a + Copy, A: Allocator,

impl<'a, T, A> Extend<&'a T> for VecDeque<T, A>

where T: 'a + Copy, A: Allocator,

impl<'a, T, A> Extend<&'a T> for avail_rust_client::ext::subxt_core::ext::scale_encode::Vec<T, A>

where T: Copy + 'a, A: Allocator,

Extend implementation that copies elements out of references before pushing them onto the Vec.

This implementation is specialized for slice iterators, where it uses copy_from_slice to append the entire slice at once.

impl<'a, T, A> Extend<&'a T> for allocator_api2::stable::vec::Vec<T, A>

where T: Copy + 'a, A: Allocator + 'a,

Extend implementation that copies elements out of references before pushing them onto the Vec.

This implementation is specialized for slice iterators, where it uses copy_from_slice to append the entire slice at once.

impl<'a, T, O> Extend<&'a bool> for BitVec<T, O>

where T: BitStore, O: BitOrder,

impl<'a, T, O> Extend<&'a T> for BitVec<T, O>

where T: BitStore, O: BitOrder,

impl<'a, T, S> Extend<&'a T> for std::collections::hash::set::HashSet<T, S>

where T: 'a + Eq + Hash + Copy, S: BuildHasher,

impl<'a, T, S, A> Extend<&'a T> for hashbrown::set::HashSet<T, S, A>

where T: 'a + Eq + Hash + Copy, S: BuildHasher, A: Allocator,

impl<'s, T> Extend<T> for SliceVec<'s, T>

impl<A> Extend<<A as Array>::Item> for SmallVec<A>

where A: Array,

impl<A> Extend<<A as Array>::Item> for TinyVec<A>

where A: Array,

impl<A> Extend<<A as Array>::Item> for tinyvec::arrayvec::ArrayVec<A>

where A: Array,

impl<A> Extend<Box<str, A>> for String

where A: Allocator,

impl<A> Extend<Box<str, A>> for String

where A: Allocator,

impl<A, EA> Extend<(A₁, A₂, …, Aₙ)> for (EA₁, EA₂, …, EAₙ)

where EA: Extend<A>,

This trait is implemented for tuples up to twelve items long. The impls for 1- and 3- through 12-ary tuples were stabilized after 2-tuples, in 1.85.0.

impl<Fut> Extend<Fut> for FuturesOrdered<Fut>

where Fut: Future,

impl<Fut> Extend<Fut> for FuturesUnordered<Fut>

impl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>

where K: Ord, A: Allocator + Clone,

impl<K, V, S> Extend<(K, V)> for std::collections::hash::map::HashMap<K, V, S>

where K: Eq + Hash, S: BuildHasher,

Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.

impl<K, V, S> Extend<(K, V)> for LiteMap<K, V, S>

where K: Ord, S: StoreBulkMut<K, V>,

impl<K, V, S, A> Extend<(K, V)> for hashbrown::map::HashMap<K, V, S, A>

where K: Eq + Hash, S: BuildHasher, A: Allocator,

Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.

impl<L, R, A> Extend<A> for Either<L, R>

where L: Extend<A>, R: Extend<A>,

impl<P> Extend<P> for PathBuf

where P: AsRef<Path>,

impl<St> Extend<St> for SelectAll<St>

where St: Stream + Unpin,

impl<T> Extend<(Option<HeaderName>, T)> for HeaderMap<T>

impl<T> Extend<(HeaderName, T)> for HeaderMap<T>

impl<T, A> Extend<T> for BTreeSet<T, A>

where T: Ord, A: Allocator + Clone,

impl<T, A> Extend<T> for BinaryHeap<T, A>

where T: Ord, A: Allocator,

impl<T, A> Extend<T> for LinkedList<T, A>

where A: Allocator,

impl<T, A> Extend<T> for VecDeque<T, A>

where A: Allocator,

impl<T, A> Extend<T> for avail_rust_client::ext::subxt_core::ext::scale_encode::Vec<T, A>

where A: Allocator,

impl<T, A> Extend<T> for allocator_api2::stable::vec::Vec<T, A>

where A: Allocator,

impl<T, L> Extend<(T, L)> for Targets

where T: Into<String>, L: Into<LevelFilter>,

impl<T, O> Extend<bool> for BitVec<T, O>

where T: BitStore, O: BitOrder,

Bit-Vector Extension

This extends a bit-vector from anything that produces individual bits.

Original

impl<T> Extend<T> for Vec<T>

Notes

This .extend() call is the second-slowest possible way to append bits into a bit-vector, faster only than calling iter.for_each(|bit| bv.push(bit)). DO NOT use this if you have any other choice.

If you are extending a bit-vector from the contents of a bit-slice, then you should use .extend_from_bitslice() instead. That method is specialized to perform upfront allocation and, where possible, use a batch copy rather than copying each bit individually from the source into the bit-vector.

impl<T, O> Extend<T> for BitVec<T, O>

where T: BitStore, O: BitOrder,

impl<T, S> Extend<T> for std::collections::hash::set::HashSet<T, S>

where T: Eq + Hash, S: BuildHasher,

impl<T, S, A> Extend<T> for hashbrown::set::HashSet<T, S, A>

where T: Eq + Hash, S: BuildHasher, A: Allocator,

impl<T, const CAP: usize> Extend<T> for arrayvec::arrayvec::ArrayVec<T, CAP>

Extend the ArrayVec with an iterator.

Panics if extending the vector exceeds its capacity.