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]);Run
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));Run
Required methods
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = A>,
[src]
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = A>,
[src]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);Run
Provided methods
fn extend_reserve(&mut self, additional: usize)
[src]
fn extend_reserve(&mut self, additional: usize)
[src]Reserves capacity in a collection for the given number of additional elements.
The default implementation does nothing.
Implementors
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.
Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.