1.4.0  Â· [ source ](../../src/std/collections/hash/map.rs.html#3157-3177) Â§

###  impl<'a, K, V, S> [ Extend ](../iter/trait.Extend.html "trait
std::iter::Extend") <( [ &'a K ](../primitive.reference.html) , [ &'a V
](../primitive.reference.html) )> for [ HashMap ](hash_map/struct.HashMap.html
"struct std::collections::hash_map::HashMap") <K, V, S>

where K: [ Eq ](../cmp/trait.Eq.html "trait std::cmp::Eq") \+ [ Hash
](../hash/trait.Hash.html "trait std::hash::Hash") \+ [ Copy
](../marker/trait.Copy.html "trait std::marker::Copy") , V: [ Copy
](../marker/trait.Copy.html "trait std::marker::Copy") , S: [ BuildHasher
](../hash/trait.BuildHasher.html "trait std::hash::BuildHasher") ,

[ source ](../../src/std/collections/hash/map.rs.html#3164-3166) Â§

####  fn [ extend ](../iter/trait.Extend.html#tymethod.extend) <T: [
IntoIterator ](../iter/trait.IntoIterator.html "trait
std::iter::IntoIterator") <Item = ( [ &'a K ](../primitive.reference.html) , [
&'a V ](../primitive.reference.html) )>>(&mut self, iter: T)

Extends a collection with the contents of an iterator. [ Read more
](../iter/trait.Extend.html#tymethod.extend)

[ source ](../../src/std/collections/hash/map.rs.html#3169-3171) Â§

####  fn [ extend_one ](../iter/trait.Extend.html#method.extend_one) (&mut
self, (k, v): ( [ &'a K ](../primitive.reference.html) , [ &'a V
](../primitive.reference.html) ))

ð¬  This is a nightly-only experimental API. ( ` extend_one ` [ #72631
](https://github.com/rust-lang/rust/issues/72631) )

Extends a collection with exactly one element.

[ source ](../../src/std/collections/hash/map.rs.html#3174-3176) Â§

####  fn [ extend_reserve ](../iter/trait.Extend.html#method.extend_reserve)
(&mut self, additional: [ usize ](../primitive.usize.html) )

ð¬  This is a nightly-only experimental API. ( ` extend_one ` [ #72631
](https://github.com/rust-lang/rust/issues/72631) )

Reserves capacity in a collection for the given number of additional elements.
[ Read more ](../iter/trait.Extend.html#method.extend_reserve)

[ source ](../../src/std/collections/hash/map.rs.html#3135-3154) Â§

###  impl<K, V, S> [ Extend ](../iter/trait.Extend.html "trait
std::iter::Extend") < [ (K, V) ](../primitive.tuple.html) > for [ HashMap
](hash_map/struct.HashMap.html "struct std::collections::hash_map::HashMap")
<K, V, S>

where K: [ Eq ](../cmp/trait.Eq.html "trait std::cmp::Eq") \+ [ Hash
](../hash/trait.Hash.html "trait std::hash::Hash") , S: [ BuildHasher
](../hash/trait.BuildHasher.html "trait std::hash::BuildHasher") ,

Inserts all new key-values from the iterator and replaces values with existing
keys with new values returned from the iterator.

[ source ](../../src/std/collections/hash/map.rs.html#3141-3143) Â§

####  fn [ extend ](../iter/trait.Extend.html#tymethod.extend) <T: [
IntoIterator ](../iter/trait.IntoIterator.html "trait
std::iter::IntoIterator") <Item = [ (K, V) ](../primitive.tuple.html) >>(&mut
self, iter: T)

Extends a collection with the contents of an iterator. [ Read more
](../iter/trait.Extend.html#tymethod.extend)

[ source ](../../src/std/collections/hash/map.rs.html#3146-3148) Â§

####  fn [ extend_one ](../iter/trait.Extend.html#method.extend_one) (&mut
self, (k, v): [ (K, V) ](../primitive.tuple.html) )

ð¬  This is a nightly-only experimental API. ( ` extend_one ` [ #72631
](https://github.com/rust-lang/rust/issues/72631) )

Extends a collection with exactly one element.

[ source ](../../src/std/collections/hash/map.rs.html#3151-3153) Â§

####  fn [ extend_reserve ](../iter/trait.Extend.html#method.extend_reserve)
(&mut self, additional: [ usize ](../primitive.usize.html) )

ð¬  This is a nightly-only experimental API. ( ` extend_one ` [ #72631
](https://github.com/rust-lang/rust/issues/72631) )

Reserves capacity in a collection for the given number of additional elements.
[ Read more ](../iter/trait.Extend.html#method.extend_reserve)