Trait Extend

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) { ... }
}

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>,

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

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one #72631)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one #72631)

Reserves capacity in a collection for the given number of additional elements.

The default implementation does nothing.

Object Safety

This trait is not object safe.

Implementors

impl Extend<char> for String

impl Extend<()> for ()

impl Extend<OsString> for OsString

impl Extend<String> for String

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

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

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

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

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

impl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>

where K: Ord + Copy, V: Copy, A: Allocator + Clone,

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S>

where K: Eq + Hash + Copy, V: Copy, S: BuildHasher,

impl<'a, T, A> Extend<&'a T> for BinaryHeap<T, A>

where T: 'a + Ord + Copy, A: Allocator,

impl<'a, T, A> Extend<&'a T> for BTreeSet<T, A>

where T: 'a + Ord + Copy, A: Allocator + Clone,

impl<'a, T, A> Extend<&'a T> for LinkedList<T, A>

where T: 'a + Copy, A: Allocator,

impl<'a, T, A> Extend<&'a T> for VecDeque<T, A>

where T: 'a + Copy, A: Allocator,

impl<'a, T, A> Extend<&'a T> for Vec<T, A>

where T: Copy + 'a, A: Allocator,

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> Extend<Box<str, A>> for String

where A: Allocator,

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

where ExtendA: Extend<A>, ExtendB: Extend<B>,

impl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>

where K: Ord, A: Allocator + Clone,

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

impl<P: AsRef<Path>> Extend<P> for PathBuf

impl<T, A> Extend<T> for BinaryHeap<T, A>

where T: Ord, A: Allocator,

impl<T, A> Extend<T> for BTreeSet<T, A>

where T: Ord, A: Allocator + Clone,

impl<T, A> Extend<T> for LinkedList<T, A>

where A: Allocator,

impl<T, A> Extend<T> for VecDeque<T, A>

where A: Allocator,

impl<T, A> Extend<T> for Vec<T, A>

where A: Allocator,

impl<T, S> Extend<T> for HashSet<T, S>

where T: Eq + Hash, S: BuildHasher,