Trait std::iter::IntoIterator1.0.0[−][src]

pub trait IntoIterator {
    type Item;
    type IntoIter: Iterator;
    fn into_iter(self) -> Self::IntoIter;
}
Expand description

Conversion into an Iterator.

By implementing IntoIterator for a type, you define how it will be converted to an iterator. This is common for types which describe a collection of some kind.

One benefit of implementing IntoIterator is that your type will work with Rust’s for loop syntax.

See also: FromIterator.

Examples

Basic usage:

let v = vec![1, 2, 3];
let mut iter = v.into_iter();

assert_eq!(Some(1), iter.next());
assert_eq!(Some(2), iter.next());
assert_eq!(Some(3), iter.next());
assert_eq!(None, iter.next());
Run

Implementing IntoIterator for your type:

// 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);
    }
}

// and we'll implement IntoIterator
impl IntoIterator for MyCollection {
    type Item = i32;
    type IntoIter = std::vec::IntoIter<Self::Item>;

    fn into_iter(self) -> Self::IntoIter {
        self.0.into_iter()
    }
}

// Now we can make a new collection...
let mut c = MyCollection::new();

// ... add some stuff to it ...
c.add(0);
c.add(1);
c.add(2);

// ... and then turn it into an Iterator:
for (i, n) in c.into_iter().enumerate() {
    assert_eq!(i as i32, n);
}
Run

It is common to use IntoIterator as a trait bound. This allows the input collection type to change, so long as it is still an iterator. Additional bounds can be specified by restricting on Item:

fn collect_as_strings<T>(collection: T) -> Vec<String>
where
    T: IntoIterator,
    T::Item: std::fmt::Debug,
{
    collection
        .into_iter()
        .map(|item| format!("{:?}", item))
        .collect()
}
Run

Associated Types

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Required methods

Creates an iterator from a value.

See the module-level documentation for more.

Examples

Basic usage:

let v = vec![1, 2, 3];
let mut iter = v.into_iter();

assert_eq!(Some(1), iter.next());
assert_eq!(Some(2), iter.next());
assert_eq!(Some(3), iter.next());
assert_eq!(None, iter.next());
Run

Implementations on Foreign Types

Creates a consuming iterator, that is, one that moves each key-value pair out of the map in arbitrary order. The map cannot be used after calling this.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

// Not possible with .iter()
let vec: Vec<(&str, i32)> = map.into_iter().collect();
Run

Creates a consuming iterator, that is, one that moves each value out of the set in arbitrary order. The set cannot be used after calling this.

Examples

use hashbrown::HashSet;
let mut set = HashSet::new();
set.insert("a".to_string());
set.insert("b".to_string());

// Not possible to collect to a Vec<String> with a regular `.iter()`.
let v: Vec<String> = set.into_iter().collect();

// Will print in an arbitrary order.
for x in &v {
    println!("{}", x);
}
Run

Implementors