Trait std::iter::Extend

pub trait Extend<A> {
    fn extend<T>(&mut self, iter: T) where T: IntoIterator<Item=A>;
}

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

// You can extend a String with some chars:
let mut message = String::from("abc");

message.extend(['d', 'e', 'f'].iter());

assert_eq!("abcdef", &message);

Implementors

• impl<T> Extend<T> for std::collections::binary_heap::BinaryHeap<T> where T: Ord
• impl<'a, T> Extend<&'a T> for std::collections::binary_heap::BinaryHeap<T> where T: 'a + Copy + Ord
• impl<K, V> Extend<(K, V)> for std::collections::btree_map::BTreeMap<K, V> where K: Ord
• impl<'a, K, V> Extend<(&'a K, &'a V)> for std::collections::btree_map::BTreeMap<K, V> where K: Copy + Ord,
        V: Copy
• impl<T> Extend<T> for std::collections::btree_set::BTreeSet<T> where T: Ord
• impl<'a, T> Extend<&'a T> for std::collections::btree_set::BTreeSet<T> where T: 'a + Copy + Ord
• impl<E> Extend<E> for collections::enum_set::EnumSet<E> where E: CLike
• impl<'a, E> Extend<&'a E> for collections::enum_set::EnumSet<E> where E: 'a + CLike + Copy
• impl<T> Extend<T> for std::collections::linked_list::LinkedList<T>
• impl<'a, T> Extend<&'a T> for std::collections::linked_list::LinkedList<T> where T: 'a + Copy
• impl Extend<char> for std::string::String
• impl<'a> Extend<&'a char> for std::string::String
• impl<'a> Extend<&'a str> for std::string::String
• impl Extend<String> for std::string::String
• impl<T> Extend<T> for std::vec::Vec<T>
• impl<'a, T> Extend<&'a T> for std::vec::Vec<T> where T: 'a + Copy
• impl<A> Extend<A> for std::collections::vec_deque::VecDeque<A>
• impl<'a, T> Extend<&'a T> for std::collections::vec_deque::VecDeque<T> where T: 'a + Copy
• impl<K, V, S> Extend<(K, V)> for std::collections::HashMap<K, V, S> where K: Eq + Hash,
        S: BuildHasher
• impl<'a, K, V, S> Extend<(&'a K, &'a V)> for std::collections::HashMap<K, V, S> where K: Eq + Hash + Copy,
        V: Copy,
        S: BuildHasher
• impl<T, S> Extend<T> for std::collections::HashSet<T, S> where T: Eq + Hash, S: BuildHasher
• impl<'a, T, S> Extend<&'a T> for std::collections::HashSet<T, S> where T: 'a + Eq + Hash + Copy,
        S: BuildHasher
• impl<P: AsRef<Path>> Extend<P> for PathBuf