pub trait IntoIterator {
    type Item;
    type IntoIter: Iterator
    where
        <Self::IntoIter as Iterator>::Item == Self::Item
; 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()
}

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 = [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());

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 std::collections::HashMap;

let map = HashMap::from([
    ("a", 1),
    ("b", 2),
    ("c", 3),
]);

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

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 std::collections::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}");
}

Creates a consuming iterator, that is, one that moves each value out of the array (from start to end). The array cannot be used after calling this unless T implements Copy, so the whole array is copied.

Arrays have special behavior when calling .into_iter() prior to the 2021 edition – see the array Editions section for more information.

Consumes the list into an iterator yielding elements by value.

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

Examples

Basic usage:

use std::collections::BinaryHeap;
let heap = BinaryHeap::from([1, 2, 3, 4]);

// Print 1, 2, 3, 4 in arbitrary order
for x in heap.into_iter() {
    // x has type i32, not &i32
    println!("{x}");
}

Consumes the deque into a front-to-back iterator yielding elements by value.

Gets an iterator for moving out the BTreeSet’s contents.

Examples
use std::collections::BTreeSet;

let set = BTreeSet::from([1, 2, 3, 4]);

let v: Vec<_> = set.into_iter().collect();
assert_eq!(v, [1, 2, 3, 4]);

Creates a consuming iterator, that is, one that moves each value out of the vector (from start to end). The vector cannot be used after calling this.

Examples
let v = vec!["a".to_string(), "b".to_string()];
for s in v.into_iter() {
    // s has type String, not &String
    println!("{s}");
}

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);
}

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();

Implementors

Iterating over the elements of a set.

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

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

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

impl<'a> IntoIterator for &'a PathBuf

impl<'a> IntoIterator for &'a Path

impl<'a> IntoIterator for &'a UnixListener

impl<'f> IntoIterator for &'f Layout

impl<'a, K, V> IntoIterator for &'a BoxedSlice<K, V> where
    K: EntityRef

impl<'a, K, V> IntoIterator for &'a mut BoxedSlice<K, V> where
    K: EntityRef

impl<K, V> IntoIterator for PrimaryMap<K, V> where
    K: EntityRef

impl<'a, K, V> IntoIterator for &'a PrimaryMap<K, V> where
    K: EntityRef

impl<'a, K, V> IntoIterator for &'a mut PrimaryMap<K, V> where
    K: EntityRef

impl<'a, K, V> IntoIterator for &'a SparseMap<K, V> where
    K: EntityRef,
    V: SparseMapValue<K>, 

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

impl<T> IntoIterator for Receiver<T>

impl<'a, Fut: Unpin> IntoIterator for &'a FuturesUnordered<Fut>

impl<'a, Fut: Unpin> IntoIterator for &'a mut FuturesUnordered<Fut>

impl<Fut: Unpin> IntoIterator for FuturesUnordered<Fut>

impl<St: Stream + Unpin> IntoIterator for SelectAll<St>

impl<'a, St: Stream + Unpin> IntoIterator for &'a SelectAll<St>

impl<'a, St: Stream + Unpin> IntoIterator for &'a mut SelectAll<St>

impl<T, N> IntoIterator for GenericArray<T, N> where
    N: ArrayLength<T>, 

impl<'a, T: 'a, N> IntoIterator for &'a GenericArray<T, N> where
    N: ArrayLength<T>, 

impl<'a, T: 'a, N> IntoIterator for &'a mut GenericArray<T, N> where
    N: ArrayLength<T>, 

impl<'a, K, V, S, A: Allocator + Clone> IntoIterator for &'a HashMap<K, V, S, A>

impl<'a, K, V, S, A: Allocator + Clone> IntoIterator for &'a mut HashMap<K, V, S, A>

impl<K, V, S, A: Allocator + Clone> IntoIterator for HashMap<K, V, S, A>

impl<'a, T, S, A: Allocator + Clone> IntoIterator for &'a HashSet<T, S, A>

impl<T, S, A: Allocator + Clone> IntoIterator for HashSet<T, S, A>

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

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

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

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

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

impl<'a, K, I, F> IntoIterator for &'a GroupBy<K, I, F> where
    I: Iterator,
    I::Item: 'a,
    F: FnMut(&I::Item) -> K,
    K: PartialEq

impl<'a, I> IntoIterator for &'a IntoChunks<I> where
    I: Iterator,
    I::Item: 'a, 

impl<'a, I> IntoIterator for &'a RcIter<I> where
    I: Iterator

impl<'a, K: Hash + Eq, V, S: BuildHasher> IntoIterator for &'a LinkedHashMap<K, V, S>

impl<'a, K: Hash + Eq, V, S: BuildHasher> IntoIterator for &'a mut LinkedHashMap<K, V, S>

impl<K: Hash + Eq, V, S: BuildHasher> IntoIterator for LinkedHashMap<K, V, S>

impl<K: Eq + Hash, V, S: BuildHasher> IntoIterator for LruCache<K, V, S>

impl<'a, K: Eq + Hash, V, S: BuildHasher> IntoIterator for &'a LruCache<K, V, S>

impl<'a, K: Eq + Hash, V, S: BuildHasher> IntoIterator for &'a mut LruCache<K, V, S>

impl<'a> IntoIterator for &'a SetMatches

impl<'a> IntoIterator for &'a SetMatches

impl<'a> IntoIterator for &'a Utf8Sequence

impl<'context, Context: Context> IntoIterator for &'context EventVec<'context, Context>

impl<'a> IntoIterator for &'a Map<String, Value>

impl<'a> IntoIterator for &'a mut Map<String, Value>

impl<'a, E: Exfiltrator> IntoIterator for &'a mut SignalsInfo<E>

impl<T> IntoIterator for Slab<T>

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

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

impl<A: Array> IntoIterator for SmallVec<A>

impl<'a, A: Array> IntoIterator for &'a SmallVec<A>

impl<'a, A: Array> IntoIterator for &'a mut SmallVec<A>

impl<'a> IntoIterator for &'a Fields

impl<'a> IntoIterator for &'a mut Fields

impl<T, P> IntoIterator for Punctuated<T, P>

impl<'a, T, P> IntoIterator for &'a Punctuated<T, P>

impl<'a, T, P> IntoIterator for &'a mut Punctuated<T, P>

impl<'a> IntoIterator for &'a Error

impl<'a, T: Send + 'a> IntoIterator for &'a mut CachedThreadLocal<T>

impl<T: Send> IntoIterator for ThreadLocal<T>

impl<'a, T: Send + Sync> IntoIterator for &'a ThreadLocal<T>

impl<'a, T: Send> IntoIterator for &'a mut ThreadLocal<T>

impl<A: Array> IntoIterator for ArrayVec<A>

impl<'a, A: Array> IntoIterator for &'a mut ArrayVec<A>

impl<'a, A: Array> IntoIterator for &'a ArrayVec<A>

impl<'s, T> IntoIterator for SliceVec<'s, T>

impl<A: Array> IntoIterator for TinyVec<A>

impl<'a, A: Array> IntoIterator for &'a mut TinyVec<A>

impl<'a, A: Array> IntoIterator for &'a TinyVec<A>

impl<'a> IntoIterator for &'a Map<String, Value>

impl<'a> IntoIterator for &'a mut Map<String, Value>

impl<'a> IntoIterator for &'a FieldSet

impl<'a> IntoIterator for &'a Targets

impl<'a> IntoIterator for &'a Name

impl<T> IntoIterator for VecMap<T>

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

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

impl<'a> IntoIterator for LocalsReader<'a>

impl<'a> IntoIterator for OperatorsReader<'a>