Trait IntoIterator

pub trait IntoIterator {
    type Item;
    type IntoIter: Iterator<Item = Self::Item>;

    // Required method
    fn into_iter(self) -> Self::IntoIter;
}

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 = [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());

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);
}

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()
}

Required Associated Types

type Item

The type of the elements being iterated over.

type IntoIter: Iterator<Item = Self::Item>

Which kind of iterator are we turning this into?

Required Methods

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

See the module-level documentation for more.

Examples

let v = [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());

Implementors

impl<'a> IntoIterator for &'a UnixListener

type Item = Result<UnixStream, Error>

type IntoIter = Incoming<'a>

impl<'a> IntoIterator for &'a Path

type Item = &'a OsStr

type IntoIter = Iter<'a>

impl<'a> IntoIterator for &'a PathBuf

type Item = &'a OsStr

type IntoIter = Iter<'a>

impl<'a, I, A> IntoIterator for &'a Box<[I], A>

where A: Allocator,

type IntoIter = Iter<'a, I>

type Item = &'a I

impl<'a, I, A> IntoIterator for &'a mut Box<[I], A>

where A: Allocator,

type IntoIter = IterMut<'a, I>

type Item = &'a mut I

impl<'a, K, V, A> IntoIterator for &'a BTreeMap<K, V, A>

where A: Allocator + Clone,

type Item = (&'a K, &'a V)

type IntoIter = Iter<'a, K, V>

impl<'a, K, V, A> IntoIterator for &'a mut BTreeMap<K, V, A>

where A: Allocator + Clone,

type Item = (&'a K, &'a mut V)

type IntoIter = IterMut<'a, K, V>

impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S>

type Item = (&'a K, &'a V)

type IntoIter = Iter<'a, K, V>

impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S>

type Item = (&'a K, &'a mut V)

type IntoIter = IterMut<'a, K, V>

impl<'a, T> IntoIterator for &'a Option<T>

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T> IntoIterator for &'a [T]

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T> IntoIterator for &'a scale_info::prelude::sync::mpmc::Receiver<T>

type Item = T

type IntoIter = Iter<'a, T>

impl<'a, T> IntoIterator for &'a scale_info::prelude::sync::mpsc::Receiver<T>

type Item = T

type IntoIter = Iter<'a, T>

impl<'a, T> IntoIterator for &'a mut Option<T>

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<'a, T> IntoIterator for &'a mut [T]

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

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

where A: Allocator,

type Item = &'a T

type IntoIter = Iter<'a, T>

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

where A: Allocator + Clone,

type Item = &'a T

type IntoIter = Iter<'a, T>

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

where A: Allocator,

type Item = &'a T

type IntoIter = Iter<'a, T>

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

where A: Allocator,

type Item = &'a T

type IntoIter = Iter<'a, T>

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

where A: Allocator,

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T, A> IntoIterator for &'a mut LinkedList<T, A>

where A: Allocator,

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<'a, T, A> IntoIterator for &'a mut VecDeque<T, A>

where A: Allocator,

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<'a, T, A> IntoIterator for &'a mut Vec<T, A>

where A: Allocator,

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<'a, T, E> IntoIterator for &'a Result<T, E>

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T, E> IntoIterator for &'a mut Result<T, E>

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<'a, T, S> IntoIterator for &'a HashSet<T, S>

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T, const CAP: usize> IntoIterator for &'a ArrayVec<T, CAP>

where T: 'a,

Iterate the ArrayVec with references to each element.

use arrayvec::ArrayVec;

let array = ArrayVec::from([1, 2, 3]);

for elt in &array {
    // ...
}

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T, const CAP: usize> IntoIterator for &'a mut ArrayVec<T, CAP>

where T: 'a,

Iterate the ArrayVec with mutable references to each element.

use arrayvec::ArrayVec;

let mut array = ArrayVec::from([1, 2, 3]);

for elt in &mut array {
    // ...
}

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<'a, T, const N: usize> IntoIterator for &'a [T; N]

type Item = &'a T

type IntoIter = Iter<'a, T>

impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N]

type Item = &'a mut T

type IntoIter = IterMut<'a, T>

impl<A> IntoIterator for Range<A>

where A: Step,

type Item = A

type IntoIter = IterRange<A>

impl<A> IntoIterator for RangeFrom<A>

where A: Step,

type Item = A

type IntoIter = IterRangeFrom<A>

impl<A> IntoIterator for RangeInclusive<A>

where A: Step,

type Item = A

type IntoIter = IterRangeInclusive<A>

impl<I> IntoIterator for I

where I: Iterator,

type Item = <I as Iterator>::Item

type IntoIter = I

impl<I, A> IntoIterator for Box<[I], A>

where A: Allocator,

type IntoIter = IntoIter<I, A>

type Item = I

impl<K, V, A> IntoIterator for BTreeMap<K, V, A>

where A: Allocator + Clone,

type Item = (K, V)

type IntoIter = IntoIter<K, V, A>

impl<K, V, S> IntoIterator for HashMap<K, V, S>

type Item = (K, V)

type IntoIter = IntoIter<K, V>

impl<T> IntoIterator for Option<T>

type Item = T

type IntoIter = IntoIter<T>

impl<T> IntoIterator for scale_info::prelude::sync::mpmc::Receiver<T>

type Item = T

type IntoIter = IntoIter<T>

impl<T> IntoIterator for scale_info::prelude::sync::mpsc::Receiver<T>

type Item = T

type IntoIter = IntoIter<T>

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

where A: Allocator,

type Item = T

type IntoIter = IntoIter<T, A>

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

where A: Allocator + Clone,

type Item = T

type IntoIter = IntoIter<T, A>

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

where A: Allocator,

type Item = T

type IntoIter = IntoIter<T, A>

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

where A: Allocator,

type Item = T

type IntoIter = IntoIter<T, A>

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

where A: Allocator,

type Item = T

type IntoIter = IntoIter<T, A>

impl<T, E> IntoIterator for Result<T, E>

type Item = T

type IntoIter = IntoIter<T>

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

type Item = T

type IntoIter = IntoIter<T>

impl<T, const CAP: usize> IntoIterator for ArrayVec<T, CAP>

Iterate the ArrayVec with each element by value.

The vector is consumed by this operation.

use arrayvec::ArrayVec;

for elt in ArrayVec::from([1, 2, 3]) {
    // ...
}

type Item = T

type IntoIter = IntoIter<T, CAP>

impl<T, const N: usize> IntoIterator for [T; N]

type Item = T

type IntoIter = IntoIter<T, N>