Trait std::iter::Extend  1.0.0[−][src]
pub trait Extend<A> {
    fn extend<T>(&mut self, iter: T)
    where
        T: IntoIterator<Item = A>;
    fn extend_one(&mut self, item: A) { ... }
    fn extend_reserve(&mut self, additional: usize) { ... }
}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
fn 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
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
fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
Reserves capacity in a collection for the given number of additional elements.
The default implementation does nothing.
Implementors
impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S> where
    K: Eq + Hash + Copy,
    V: Copy,
    S: BuildHasher, 
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, S> Extend<&'a T> for HashSet<T, S> where
    T: 'a + Eq + Hash + Copy,
    S: BuildHasher, 
impl<A, B, ExtendA, ExtendB> Extend<(A, B)> for (ExtendA, ExtendB) where
    ExtendA: Extend<A>,
    ExtendB: Extend<B>, 
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.