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_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one)Extends a collection with exactly one element.
fn extend_reserve(&mut self, additional: usize)
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.
Implementations on Foreign Types
extend_one)Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.
extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)Allows to extend a tuple of collections that also implement Extend.
See also: Iterator::unzip
Examples
let mut tuple = (vec![0], vec![1]);
tuple.extend([(2, 3), (4, 5), (6, 7)]);
assert_eq!(tuple.0, [0, 2, 4, 6]);
assert_eq!(tuple.1, [1, 3, 5, 7]);
// also allows for arbitrarily nested tuples as elements
let mut nested_tuple = (vec![1], (vec![2], vec![3]));
nested_tuple.extend([(4, (5, 6)), (7, (8, 9))]);
let (a, (b, c)) = nested_tuple;
assert_eq!(a, [1, 4, 7]);
assert_eq!(b, [2, 5, 8]);
assert_eq!(c, [3, 6, 9]);extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)extend_one)Implementors
impl<'a, K, V> Extend<(&'a K, &'a V)> for BTreeMap<K, V> where
K: Ord + Copy,
V: Copy,
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.