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) { ... }
}
Available on non-crate feature miri-test-libstd only.
Expand description

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§

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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

Basic usage:

// 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§

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fn extend_one(&mut self, item: A)

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

Extends a collection with exactly one element.

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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.

Implementors§

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impl Extend<char> for CompactString

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impl Extend<char> for String

Available on non-no_global_oom_handling only.
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impl Extend<u8> for BytesMut

1.28.0 · source§

impl Extend<()> for ()

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impl Extend<usize> for FixedBitSet

Sets the bit at index i to true for each item i in the input src.

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impl Extend<Bytes> for BytesMut

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impl Extend<CompactString> for CompactString

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impl Extend<CompactString> for String

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impl Extend<Box<str, Global>> for CompactString

1.45.0 · source§

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

Available on non-no_global_oom_handling only.
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impl Extend<String> for CompactString

1.4.0 · source§

impl Extend<String> for String

Available on non-no_global_oom_handling only.
1.52.0 · source§

impl Extend<OsString> for OsString

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impl Extend<EventMask> for EventMask

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impl Extend<Flags> for Flags

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impl Extend<FsyncFlags> for FsyncFlags

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impl Extend<TimeoutFlags> for TimeoutFlags

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impl Extend<WatchMask> for WatchMask

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

1.2.0 · source§

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

Available on non-no_global_oom_handling only.
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impl<'a> Extend<&'a str> for CompactString

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

Available on non-no_global_oom_handling only.
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impl<'a> Extend<&'a u8> for BytesMut

1.52.0 · source§

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

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

1.19.0 · source§

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

Available on non-no_global_oom_handling only.
1.52.0 · source§

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

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

1.2.0 · source§

impl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>where K: Ord + Copy, V: Copy, A: Allocator + Clone,

1.4.0 · source§

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for kvarn::prelude::HashMap<K, V, S>where K: Eq + Hash + Copy, V: Copy, S: BuildHasher,

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impl<'a, K, V, S> Extend<(&'a K, &'a V)> for IndexMap<K, V, S>where K: Hash + Eq + Copy, V: Copy, S: BuildHasher,

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impl<'a, K, V, S, A> Extend<&'a (K, V)> for HashMap<K, V, S, A>where K: Eq + Hash + Copy, V: Copy, S: BuildHasher, A: Allocator + Clone,

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

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impl<'a, K, V, S, A> Extend<&'a (K, V)> for HashMap<K, V, S, A>where K: Eq + Hash + Copy, V: Copy, S: BuildHasher, A: Allocator + Clone,

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

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impl<'a, K, V, S, A> Extend<(&'a K, &'a V)> for HashMap<K, V, S, A>where K: Eq + Hash + Copy, V: Copy, S: BuildHasher, A: Allocator + Clone,

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

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impl<'a, K, V, S, A> Extend<(&'a K, &'a V)> for HashMap<K, V, S, A>where K: Eq + Hash + Copy, V: Copy, S: BuildHasher, A: Allocator + Clone,

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

1.2.0 · source§

impl<'a, T> Extend<&'a T> for BinaryHeap<T>where T: 'a + Ord + Copy,

1.2.0 · source§

impl<'a, T> Extend<&'a T> for LinkedList<T>where T: 'a + Copy,

1.2.0 · source§

impl<'a, T, A> Extend<&'a T> for BTreeSet<T, A>where T: 'a + Ord + Copy, A: Allocator + Clone,

1.2.0 · source§

impl<'a, T, A> Extend<&'a T> for VecDeque<T, A>where T: 'a + Copy, A: Allocator,

1.2.0 · source§

impl<'a, T, A> Extend<&'a T> for Vec<T, A>where T: Copy + 'a, A: Allocator + 'a,

Available on non-no_global_oom_handling only.

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.

1.4.0 · source§

impl<'a, T, S> Extend<&'a T> for std::collections::hash::set::HashSet<T, S>where T: 'a + Eq + Hash + Copy, S: BuildHasher,

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impl<'a, T, S> Extend<&'a T> for IndexSet<T, S>where T: Hash + Eq + Copy + 'a, S: BuildHasher,

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impl<'a, T, S, A> Extend<&'a T> for HashSet<T, S, A>where T: 'a + Eq + Hash + Copy, S: BuildHasher, A: Allocator + Clone,

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impl<'a, T, S, A> Extend<&'a T> for HashSet<T, S, A>where T: 'a + Eq + Hash + Copy, S: BuildHasher, A: Allocator + Clone,

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

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impl<A> Extend<<A as Array>::Item> for ArrayVec<A>where A: Array,

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

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

1.56.0 · source§

impl<A, B, ExtendA, ExtendB> Extend<(A, B)> for (ExtendA, ExtendB)where ExtendA: Extend<A>, ExtendB: Extend<B>,

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impl<Fut> Extend<Fut> for FuturesOrdered<Fut>where Fut: Future,

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

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impl<K, S> Extend<K> for DashSet<K, S>where K: Eq + Hash, S: BuildHasher + Clone,

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impl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>where K: Ord, A: Allocator + Clone,

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impl<K, V, S> Extend<(K, V)> for kvarn::prelude::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.

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impl<K, V, S> Extend<(K, V)> for IndexMap<K, V, S>where K: Hash + Eq, S: BuildHasher,

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impl<K, V, S> Extend<(K, V)> for DashMap<K, V, S>where K: Eq + Hash, S: BuildHasher + Clone,

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impl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A>where K: Eq + Hash, S: BuildHasher, A: Allocator + Clone,

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

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impl<K, V, S, A> Extend<(K, V)> for HashMap<K, V, S, A>where K: Eq + Hash, S: BuildHasher, A: Allocator + Clone,

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

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impl<N, E, Ty, Item> Extend<Item> for GraphMap<N, E, Ty>where Item: IntoWeightedEdge<E, NodeId = N>, N: NodeTrait, Ty: EdgeType,

Extend the graph from an iterable of edges.

Nodes are inserted automatically to match the edges.

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impl<P> Extend<P> for PathBufwhere P: AsRef<Path>,

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impl<St> Extend<St> for SelectAll<St>where St: Stream + Unpin,

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

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

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impl<T> Extend<T> for BinaryHeap<T>where T: Ord,

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impl<T> Extend<T> for LinkedList<T>

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impl<T, A> Extend<T> for BTreeSet<T, A>where T: Ord, A: Allocator + Clone,

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impl<T, A> Extend<T> for VecDeque<T, A>where A: Allocator,

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impl<T, A> Extend<T> for Vec<T, A>where A: Allocator,

Available on non-no_global_oom_handling only.
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impl<T, S> Extend<T> for std::collections::hash::set::HashSet<T, S>where T: Eq + Hash, S: BuildHasher,

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impl<T, S> Extend<T> for IndexSet<T, S>where T: Hash + Eq, S: BuildHasher,

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impl<T, S, A> Extend<T> for HashSet<T, S, A>where T: Eq + Hash, S: BuildHasher, A: Allocator + Clone,

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impl<T, S, A> Extend<T> for HashSet<T, S, A>where T: Eq + Hash, S: BuildHasher, A: Allocator + Clone,