# Trait std::iter::IntoIterator

1.0.0 · source ·

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

        // Required method
        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 = [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

## Required Associated Types§

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#### type Item

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

## Required Methods§

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#### 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());

Run

## Implementors§

1.10.0 · source§

### impl<'a> IntoIterator for &'a UnixListener

Available on Unix only.
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#### type Item = Result<UnixStream, Error>

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#### type IntoIter = Incoming<'a>

1.6.0 · source§

### impl<'a> IntoIterator for &'a Path

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#### type Item = &'a OsStr

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#### type IntoIter = Iter<'a>

1.6.0 · source§

### impl<'a> IntoIterator for &'a PathBuf

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#### type Item = &'a OsStr

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#### type IntoIter = Iter<'a>

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### impl<'a, K, V, A> IntoIterator for &'a BTreeMap<K, V, A>where A: Allocator + Clone,

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

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

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### impl<'a, K, V, A> IntoIterator for &'a mut BTreeMap<K, V, A>where A: Allocator + Clone,

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

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

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

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

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

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

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

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

1.4.0 · source§

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

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

1.1.0 · source§

### impl<'a, T> IntoIterator for &'a Receiver<T>

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#### type Item = T

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#### type IntoIter = Iter<'a, T>

1.4.0 · source§

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

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

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

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

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### impl<'a, T, A> IntoIterator for &'a BTreeSet<T, A>where A: Allocator + Clone,

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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### impl<'a, T, A> IntoIterator for &'a BinaryHeap<T, A>where A: Allocator,

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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### impl<'a, T, A> IntoIterator for &'a LinkedList<T, A>where A: Allocator,

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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### impl<'a, T, A> IntoIterator for &'a VecDeque<T, A>where A: Allocator,

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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### impl<'a, T, A> IntoIterator for &'a mut LinkedList<T, A>where A: Allocator,

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

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### impl<'a, T, A> IntoIterator for &'a mut VecDeque<T, A>where A: Allocator,

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

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### impl<'a, T, A, FH> IntoIterator for &'a Vec<T, A, FH>where A: Allocator, FH: FailureHandling,

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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### impl<'a, T, A, FH> IntoIterator for &'a mut Vec<T, A, FH>where A: Allocator, FH: FailureHandling,

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

1.4.0 · source§

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

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

1.4.0 · source§

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

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

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

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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

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#### type Item = &'a T

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#### type IntoIter = Iter<'a, T>

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

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#### type Item = &'a mut T

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#### type IntoIter = IterMut<'a, T>

const: unstable · source§

### impl<I> IntoIterator for Iwhere I: Iterator,

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#### type Item = <I as Iterator>::Item

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#### type IntoIter = I

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### impl<K, V, A> IntoIterator for BTreeMap<K, V, A>where A: Allocator + Clone,

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#### type Item = (K, V)

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#### type IntoIter = IntoIter<K, V, A>

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

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#### type Item = (K, V)

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#### type IntoIter = IntoIter<K, V>

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### impl<T> IntoIterator for Option<T>

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#### type Item = T

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#### type IntoIter = IntoIter<T>

1.1.0 · source§

### impl<T> IntoIterator for Receiver<T>

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#### type Item = T

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#### type IntoIter = IntoIter<T>

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### impl<T, A> IntoIterator for BTreeSet<T, A>where A: Allocator + Clone,

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#### type Item = T

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#### type IntoIter = IntoIter<T, A>

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### impl<T, A> IntoIterator for BinaryHeap<T, A>where A: Allocator,

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#### type Item = T

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#### type IntoIter = IntoIter<T, A>

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### impl<T, A> IntoIterator for LinkedList<T, A>where A: Allocator,

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#### type Item = T

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#### type IntoIter = IntoIter<T, A>

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### impl<T, A> IntoIterator for VecDeque<T, A>where A: Allocator,

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#### type Item = T

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#### type IntoIter = IntoIter<T, A>

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### impl<T, A, FH> IntoIterator for Vec<T, A, FH>where A: Allocator, FH: FailureHandling,

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#### type Item = T

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#### type IntoIter = IntoIter<T, A>

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

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#### type Item = T

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#### type IntoIter = IntoIter<T>

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

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#### type Item = T

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#### type IntoIter = IntoIter<T>

1.53.0 · source§

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

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#### type Item = T

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#### type IntoIter = IntoIter<T, N>