IntoIterator in core::iter - Rust
Description: Conversion into an `Iterator`.

# Trait IntoIterator

1.6.0 · 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());

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§

1.0.0 · Source

#### type Item

The type of the elements being iterated over.

1.0.0 · Source

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

Which kind of iterator are we turning this into?

## Required Methods§

1.0.0 · Source

#### 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§

1.4.0 · Source§

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

Source§

#### type Item = &'a T

Source§

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

1.0.0 · Source§

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

Source§

#### type Item = &'a T

Source§

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

1.4.0 · Source§

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

Source§

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

Source§

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

1.0.0 · Source§

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

Source§

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

Source§

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

1.4.0 · Source§

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

Source§

#### type Item = &'a T

Source§

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

1.4.0 · Source§

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

Source§

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

Source§

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

1.0.0 · Source§

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

Source§

#### type Item = &'a T

Source§

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

1.0.0 · Source§

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

Source§

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

Source§

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

Source§

### impl<A: Step> IntoIterator for Range<A>

Source§

#### type Item = A

Source§

#### type IntoIter = IterRange<A>

Source§

### impl<A: Step> IntoIterator for RangeFrom<A>

Source§

#### type Item = A

Source§

#### type IntoIter = IterRangeFrom<A>

Source§

### impl<A: Step> IntoIterator for RangeInclusive<A>

Source§

#### type Item = A

Source§

#### type IntoIter = IterRangeInclusive<A>

1.0.0 · Source§

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

Source§

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

Source§

#### type IntoIter = I

1.0.0 · Source§

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

Source§

#### type Item = T

Source§

#### type IntoIter = IntoIter<T>

1.0.0 · Source§

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

Source§

#### type Item = T

Source§

#### type IntoIter = IntoIter<T>

1.53.0 · Source§

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

Source§

#### type Item = T

Source§

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