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) { ... }
}std 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§
1.0.0 · Sourcefn extend<T>(&mut self, iter: T)where
T: IntoIterator<Item = A>,
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§
Sourcefn extend_one(&mut self, item: A)
🔬This is a nightly-only experimental API. (extend_one)
fn extend_one(&mut self, item: A)
extend_one)Extends a collection with exactly one element.
Sourcefn extend_reserve(&mut self, additional: usize)
🔬This is a nightly-only experimental API. (extend_one)
fn extend_reserve(&mut self, additional: usize)
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<char> for String
no_global_oom_handling only.impl Extend<u8> for BytesMut
impl Extend<()> for ()
impl Extend<String> for String
no_global_oom_handling only.impl Extend<OsString> for OsString
impl Extend<Bytes> for BytesMut
impl<'a> Extend<&'a char> for String
no_global_oom_handling only.impl<'a> Extend<&'a str> for String
no_global_oom_handling only.impl<'a> Extend<&'a u8> for BytesMut
impl<'a> Extend<&'a OsStr> for OsString
impl<'a> Extend<Cow<'a, str>> for String
no_global_oom_handling only.impl<'a> Extend<Cow<'a, OsStr>> for OsString
impl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>
impl<'a, K, V, S> Extend<(&'a K, &'a V)> for std::collections::hash::map::HashMap<K, V, S>
impl<'a, K, V, S> Extend<(&'a K, &'a V)> for IndexMap<K, V, S>
impl<'a, K, V, S, A> Extend<&'a (K, V)> for hashbrown::map::HashMap<K, V, S, A>
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>
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
impl<'a, T, A> Extend<&'a T> for Vec<T, A>
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.
impl<'a, T, A> Extend<&'a T> for BinaryHeap<T, A>
impl<'a, T, A> Extend<&'a T> for BTreeSet<T, A>
impl<'a, T, A> Extend<&'a T> for LinkedList<T, A>
impl<'a, T, A> Extend<&'a T> for VecDeque<T, A>
impl<'a, T, S> Extend<&'a T> for std::collections::hash::set::HashSet<T, S>
impl<'a, T, S> Extend<&'a T> for IndexSet<T, S>
impl<'a, T, S, A> Extend<&'a T> for hashbrown::set::HashSet<T, S, A>
impl<A> Extend<Box<str, A>> for Stringwhere
A: Allocator,
no_global_oom_handling only.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 CURRENT_RUSTC_VERSION.
impl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>
impl<K, V, S> Extend<(K, V)> for std::collections::hash::map::HashMap<K, V, S>
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 IndexMap<K, V, S>
impl<K, V, S, A> Extend<(K, V)> for hashbrown::map::HashMap<K, V, S, A>
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
impl<P> Extend<P> for PathBuf
impl<T, A> Extend<T> for Vec<T, A>where
A: Allocator,
no_global_oom_handling only.