# Struct hashbrown::HashMap [−] [src]

    pub struct HashMap<K, V, S = DefaultHashBuilder> { /* fields omitted */ }

A hash map implemented with quadratic probing and SIMD lookup.

The default hashing algorithm is currently `AHash`, though this is subject to change at any point in the future. This hash function is very fast for all types of keys, but this algorithm will typically not protect against attacks such as HashDoS.

The hashing algorithm can be replaced on a per-`HashMap` basis using the `default`, `with_hasher`, and `with_capacity_and_hasher` methods. Many alternative algorithms are available on crates.io, such as the `fnv` crate.

It is required that the keys implement the `Eq` and `Hash` traits, although this can frequently be achieved by using `#[derive(PartialEq, Eq, Hash)]`. If you implement these yourself, it is important that the following property holds:

    k1 == k2 -> hash(k1) == hash(k2)

In other words, if two keys are equal, their hashes must be equal.

It is a logic error for a key to be modified in such a way that the key’s hash, as determined by the `Hash` trait, or its equality, as determined by the `Eq` trait, changes while it is in the map. This is normally only possible through `Cell`, `RefCell`, global state, I/O, or unsafe code.

It is also a logic error for the `Hash` implementation of a key to panic. This is generally only possible if the trait is implemented manually. If a panic does occur then the contents of the `HashMap` may become corrupted and some items may be dropped from the table.

# Examples

    use hashbrown::HashMap;

    // Type inference lets us omit an explicit type signature (which
    // would be `HashMap<String, String>` in this example).
    let mut book_reviews = HashMap::new();

    // Review some books.
    book_reviews.insert(
        "Adventures of Huckleberry Finn".to_string(),
        "My favorite book.".to_string(),
    );
    book_reviews.insert(
        "Grimms' Fairy Tales".to_string(),
        "Masterpiece.".to_string(),
    );
    book_reviews.insert(
        "Pride and Prejudice".to_string(),
        "Very enjoyable.".to_string(),
    );
    book_reviews.insert(
        "The Adventures of Sherlock Holmes".to_string(),
        "Eye lyked it alot.".to_string(),
    );

    // Check for a specific one.
    // When collections store owned values (String), they can still be
    // queried using references (&str).
    if !book_reviews.contains_key("Les Misérables") {
        println!("We've got {} reviews, but Les Misérables ain't one.",
                 book_reviews.len());
    }

    // oops, this review has a lot of spelling mistakes, let's delete it.
    book_reviews.remove("The Adventures of Sherlock Holmes");

    // Look up the values associated with some keys.
    let to_find = ["Pride and Prejudice", "Alice's Adventure in Wonderland"];
    for &book in &to_find {
        match book_reviews.get(book) {
            Some(review) => println!("{}: {}", book, review),
            None => println!("{} is unreviewed.", book)
        }
    }

    // Look up the value for a key (will panic if the key is not found).
    println!("Review for Jane: {}", book_reviews["Pride and Prejudice"]);

    // Iterate over everything.
    for (book, review) in &book_reviews {
        println!("{}: \"{}\"", book, review);
    }

`HashMap` also implements an `Entry API`, which allows for more complex methods of getting, setting, updating and removing keys and their values:

    use hashbrown::HashMap;

    // type inference lets us omit an explicit type signature (which
    // would be `HashMap<&str, u8>` in this example).
    let mut player_stats = HashMap::new();

    fn random_stat_buff() -> u8 {
        // could actually return some random value here - let's just return
        // some fixed value for now
        42
    }

    // insert a key only if it doesn't already exist
    player_stats.entry("health").or_insert(100);

    // insert a key using a function that provides a new value only if it
    // doesn't already exist
    player_stats.entry("defence").or_insert_with(random_stat_buff);

    // update a key, guarding against the key possibly not being set
    let stat = player_stats.entry("attack").or_insert(100);
    *stat += random_stat_buff();

The easiest way to use `HashMap` with a custom key type is to derive `Eq` and `Hash`. We must also derive `PartialEq`.

    use hashbrown::HashMap;

    #[derive(Hash, Eq, PartialEq, Debug)]
    struct Viking {
        name: String,
        country: String,
    }

    impl Viking {
        /// Creates a new Viking.
        fn new(name: &str, country: &str) -> Viking {
            Viking { name: name.to_string(), country: country.to_string() }
        }
    }

    // Use a HashMap to store the vikings' health points.
    let mut vikings = HashMap::new();

    vikings.insert(Viking::new("Einar", "Norway"), 25);
    vikings.insert(Viking::new("Olaf", "Denmark"), 24);
    vikings.insert(Viking::new("Harald", "Iceland"), 12);

    // Use derived implementation to print the status of the vikings.
    for (viking, health) in &vikings {
        println!("{:?} has {} hp", viking, health);
    }

A `HashMap` with fixed list of elements can be initialized from an array:

    use hashbrown::HashMap;

    let timber_resources: HashMap<&str, i32> = [("Norway", 100), ("Denmark", 50), ("Iceland", 10)]
        .iter().cloned().collect();
    // use the values stored in map

## Implementations

### `impl<K, V, S> HashMap<K, V, S>` [src]

#### `pub const fn with_hasher(hash_builder: S) -> Self` [src]

Creates an empty `HashMap` which will use the given hash builder to hash keys.

The created map has the default initial capacity.

Warning: `hash_builder` is normally randomly generated, and is designed to allow HashMaps to be resistant to attacks that cause many collisions and very poor performance. Setting it manually using this function can expose a DoS attack vector.

The `hash_builder` passed should implement the `BuildHasher` trait for the HashMap to be useful, see its documentation for details.

# Examples

    use hashbrown::HashMap;
    use hashbrown::hash_map::DefaultHashBuilder;

    let s = DefaultHashBuilder::default();
    let mut map = HashMap::with_hasher(s);
    map.insert(1, 2);

#### `pub fn with_capacity_and_hasher(capacity: usize, hash_builder: S) -> Self` [src]

Creates an empty `HashMap` with the specified capacity, using `hash_builder` to hash the keys.

The hash map will be able to hold at least `capacity` elements without reallocating. If `capacity` is 0, the hash map will not allocate.

Warning: `hash_builder` is normally randomly generated, and is designed to allow HashMaps to be resistant to attacks that cause many collisions and very poor performance. Setting it manually using this function can expose a DoS attack vector.

The `hash_builder` passed should implement the `BuildHasher` trait for the HashMap to be useful, see its documentation for details.

# Examples

    use hashbrown::HashMap;
    use hashbrown::hash_map::DefaultHashBuilder;

    let s = DefaultHashBuilder::default();
    let mut map = HashMap::with_capacity_and_hasher(10, s);
    map.insert(1, 2);

#### `pub fn hasher(&self) -> &S` [src]

Returns a reference to the map’s `BuildHasher`.

# Examples

    use hashbrown::HashMap;
    use hashbrown::hash_map::DefaultHashBuilder;

    let hasher = DefaultHashBuilder::default();
    let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
    let hasher: &DefaultHashBuilder = map.hasher();

#### `pub fn capacity(&self) -> usize` [src]

Returns the number of elements the map can hold without reallocating.

This number is a lower bound; the `HashMap<K, V>` might be able to hold more, but is guaranteed to be able to hold at least this many.

# Examples

    use hashbrown::HashMap;
    let map: HashMap<i32, i32> = HashMap::with_capacity(100);
    assert!(map.capacity() >= 100);

#### `pub fn keys(&self) -> Keys<'_, K, V>ⓘ

### Notable traits for Keys<'a, K, V>

`impl<'a, K, V> Iterator for Keys<'a, K, V> type Item = &'a K;`
` [src]

An iterator visiting all keys in arbitrary order. The iterator element type is `&'a K`.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert("a", 1);
    map.insert("b", 2);
    map.insert("c", 3);

    for key in map.keys() {
        println!("{}", key);
    }

#### `pub fn values(&self) -> Values<'_, K, V>ⓘ

### Notable traits for Values<'a, K, V>

`impl<'a, K, V> Iterator for Values<'a, K, V> type Item = &'a V;`
` [src]

An iterator visiting all values in arbitrary order. The iterator element type is `&'a V`.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert("a", 1);
    map.insert("b", 2);
    map.insert("c", 3);

    for val in map.values() {
        println!("{}", val);
    }

#### `pub fn values_mut(&mut self) -> ValuesMut<'_, K, V>ⓘ

### Notable traits for ValuesMut<'a, K, V>

`impl<'a, K, V> Iterator for ValuesMut<'a, K, V> type Item = &'a mut V;`
` [src]

An iterator visiting all values mutably in arbitrary order. The iterator element type is `&'a mut V`.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();

    map.insert("a", 1);
    map.insert("b", 2);
    map.insert("c", 3);

    for val in map.values_mut() {
        *val = *val + 10;
    }

    for val in map.values() {
        println!("{}", val);
    }

#### `pub fn iter(&self) -> Iter<'_, K, V>ⓘ

### Notable traits for Iter<'a, K, V>

`impl<'a, K, V> Iterator for Iter<'a, K, V> type Item = (&'a K, &'a V);`
` [src]

An iterator visiting all key-value pairs in arbitrary order. The iterator element type is `(&'a K, &'a V)`.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert("a", 1);
    map.insert("b", 2);
    map.insert("c", 3);

    for (key, val) in map.iter() {
        println!("key: {} val: {}", key, val);
    }

#### `pub fn iter_mut(&mut self) -> IterMut<'_, K, V>ⓘ

### Notable traits for IterMut<'a, K, V>

`impl<'a, K, V> Iterator for IterMut<'a, K, V> type Item = (&'a K, &'a mut V);`
` [src]

An iterator visiting all key-value pairs in arbitrary order, with mutable references to the values. The iterator element type is `(&'a K, &'a mut V)`.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert("a", 1);
    map.insert("b", 2);
    map.insert("c", 3);

    // Update all values
    for (_, val) in map.iter_mut() {
        *val *= 2;
    }

    for (key, val) in &map {
        println!("key: {} val: {}", key, val);
    }

#### `pub fn len(&self) -> usize` [src]

Returns the number of elements in the map.

# Examples

    use hashbrown::HashMap;

    let mut a = HashMap::new();
    assert_eq!(a.len(), 0);
    a.insert(1, "a");
    assert_eq!(a.len(), 1);

#### `pub fn is_empty(&self) -> bool` [src]

Returns `true` if the map contains no elements.

# Examples

    use hashbrown::HashMap;

    let mut a = HashMap::new();
    assert!(a.is_empty());
    a.insert(1, "a");
    assert!(!a.is_empty());

#### `pub fn drain(&mut self) -> Drain<'_, K, V>ⓘ

### Notable traits for Drain<'a, K, V>

`impl<'a, K, V> Iterator for Drain<'a, K, V> type Item = (K, V);`
` [src]

Clears the map, returning all key-value pairs as an iterator. Keeps the allocated memory for reuse.

# Examples

    use hashbrown::HashMap;

    let mut a = HashMap::new();
    a.insert(1, "a");
    a.insert(2, "b");

    for (k, v) in a.drain().take(1) {
        assert!(k == 1 || k == 2);
        assert!(v == "a" || v == "b");
    }

    assert!(a.is_empty());

#### `pub fn retain<F>(&mut self, f: F) where
F: FnMut(&K, &mut V) -> bool,` [src]

Retains only the elements specified by the predicate.

In other words, remove all pairs `(k, v)` such that `f(&k,&mut v)` returns `false`.

# Examples

    use hashbrown::HashMap;

    let mut map: HashMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
    map.retain(|&k, _| k % 2 == 0);
    assert_eq!(map.len(), 4);

#### `pub fn drain_filter<F>(&mut self, f: F) -> DrainFilter<'_, K, V, F>ⓘ

### Notable traits for DrainFilter<'_, K, V, F>

`impl<K, V, F> Iterator for DrainFilter<'_, K, V, F> where
F: FnMut(&K, &mut V) -> bool, type Item = (K, V);`
where
F: FnMut(&K, &mut V) -> bool,` [src]

Drains elements which are true under the given predicate, and returns an iterator over the removed items.

In other words, move all pairs `(k, v)` such that `f(&k,&mut v)` returns `true` out into another iterator.

When the returned DrainedFilter is dropped, any remaining elements that satisfy the predicate are dropped from the table.

# Examples

    use hashbrown::HashMap;

    let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();
    let drained: HashMap<i32, i32> = map.drain_filter(|k, _v| k % 2 == 0).collect();

    let mut evens = drained.keys().cloned().collect::<Vec<_>>();
    let mut odds = map.keys().cloned().collect::<Vec<_>>();
    evens.sort();
    odds.sort();

    assert_eq!(evens, vec![0, 2, 4, 6]);
    assert_eq!(odds, vec![1, 3, 5, 7]);

#### `pub fn clear(&mut self)` [src]

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

# Examples

    use hashbrown::HashMap;

    let mut a = HashMap::new();
    a.insert(1, "a");
    a.clear();
    assert!(a.is_empty());

### `impl<K, V, S> HashMap<K, V, S> where
K: Eq + Hash,
S: BuildHasher,` [src]

#### `pub fn reserve(&mut self, additional: usize)` [src]

Reserves capacity for at least `additional` more elements to be inserted in the `HashMap`. The collection may reserve more space to avoid frequent reallocations.

# Panics

Panics if the new allocation size overflows `usize`.

# Examples

    use hashbrown::HashMap;
    let mut map: HashMap<&str, i32> = HashMap::new();
    map.reserve(10);

#### `pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>` [src]

Tries to reserve capacity for at least `additional` more elements to be inserted in the given `HashMap<K,V>`. The collection may reserve more space to avoid frequent reallocations.

# Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

# Examples

    use hashbrown::HashMap;
    let mut map: HashMap<&str, isize> = HashMap::new();
    map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");

#### `pub fn shrink_to_fit(&mut self)` [src]

Shrinks the capacity of the map as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

# Examples

    use hashbrown::HashMap;

    let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
    map.insert(1, 2);
    map.insert(3, 4);
    assert!(map.capacity() >= 100);
    map.shrink_to_fit();
    assert!(map.capacity() >= 2);

#### `pub fn shrink_to(&mut self, min_capacity: usize)` [src]

Shrinks the capacity of the map with a lower limit. It will drop down no lower than the supplied limit while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

This function does nothing if the current capacity is smaller than the supplied minimum capacity.

# Examples

    use hashbrown::HashMap;

    let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
    map.insert(1, 2);
    map.insert(3, 4);
    assert!(map.capacity() >= 100);
    map.shrink_to(10);
    assert!(map.capacity() >= 10);
    map.shrink_to(0);
    assert!(map.capacity() >= 2);
    map.shrink_to(10);
    assert!(map.capacity() >= 2);

#### `pub fn entry(&mut self, key: K) -> Entry<'_, K, V, S>` [src]

Gets the given key’s corresponding entry in the map for in-place manipulation.

# Examples

    use hashbrown::HashMap;

    let mut letters = HashMap::new();

    for ch in "a short treatise on fungi".chars() {
        let counter = letters.entry(ch).or_insert(0);
        *counter += 1;
    }

    assert_eq!(letters[&'s'], 2);
    assert_eq!(letters[&'t'], 3);
    assert_eq!(letters[&'u'], 1);
    assert_eq!(letters.get(&'y'), None);

#### `pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V> where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    assert_eq!(map.get(&1), Some(&"a"));
    assert_eq!(map.get(&2), None);

#### `pub fn get_key_value<Q: ?Sized>(&self, k: &Q) -> Option<(&K, &V)> where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Returns the key-value pair corresponding to the supplied key.

The supplied key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
    assert_eq!(map.get_key_value(&2), None);

#### `pub fn get_key_value_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<(&K, &mut V)> where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Returns the key-value pair corresponding to the supplied key, with a mutable reference to value.

The supplied key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    let (k, v) = map.get_key_value_mut(&1).unwrap();
    assert_eq!(k, &1);
    assert_eq!(v, &mut "a");
    *v = "b";
    assert_eq!(map.get_key_value_mut(&1), Some((&1, &mut "b")));
    assert_eq!(map.get_key_value_mut(&2), None);

#### `pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Returns `true` if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    assert_eq!(map.contains_key(&1), true);
    assert_eq!(map.contains_key(&2), false);

#### `pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V> where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Returns a mutable reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    if let Some(x) = map.get_mut(&1) {
        *x = "b";
    }
    assert_eq!(map[&1], "b");

#### `pub fn insert(&mut self, k: K, v: V) -> Option<V>` [src]

Inserts a key-value pair into the map.

If the map did not have this key present, `None` is returned.

If the map did have this key present, the value is updated, and the old value is returned. The key is not updated, though; this matters for types that can be `==` without being identical. See the module-level documentation for more.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    assert_eq!(map.insert(37, "a"), None);
    assert_eq!(map.is_empty(), false);

    map.insert(37, "b");
    assert_eq!(map.insert(37, "c"), Some("b"));
    assert_eq!(map[&37], "c");

#### `pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V> where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Removes a key from the map, returning the value at the key if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    assert_eq!(map.remove(&1), Some("a"));
    assert_eq!(map.remove(&1), None);

#### `pub fn remove_entry<Q: ?Sized>(&mut self, k: &Q) -> Option<(K, V)> where
K: Borrow<Q>,
Q: Hash + Eq,` [src]

Removes a key from the map, returning the stored key and value if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but `Hash` and `Eq` on the borrowed form must match those for the key type.

# Examples

    use hashbrown::HashMap;

    let mut map = HashMap::new();
    map.insert(1, "a");
    assert_eq!(map.remove_entry(&1), Some((1, "a")));
    assert_eq!(map.remove(&1), None);

### `impl<K, V, S> HashMap<K, V, S>` [src]

#### `pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S>` [src]

Creates a raw entry builder for the HashMap.

Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched. After this, insertions into a vacant entry still require an owned key to be provided.

Raw entries are useful for such exotic situations as:

- Hash memoization
- Deferring the creation of an owned key until it is known to be required
- Using a search key that doesn’t work with the Borrow trait
- Using custom comparison logic without newtype wrappers

Because raw entries provide much more low-level control, it’s much easier to put the HashMap into an inconsistent state which, while memory-safe, will cause the map to produce seemingly random results. Higher-level and more foolproof APIs like `entry` should be preferred when possible.

In particular, the hash used to initialized the raw entry must still be consistent with the hash of the key that is ultimately stored in the entry. This is because implementations of HashMap may need to recompute hashes when resizing, at which point only the keys are available.

Raw entries give mutable access to the keys. This must not be used to modify how the key would compare or hash, as the map will not re-evaluate where the key should go, meaning the keys may become “lost” if their location does not reflect their state. For instance, if you change a key so that the map now contains keys which compare equal, search may start acting erratically, with two keys randomly masking each other. Implementations are free to assume this doesn’t happen (within the limits of memory-safety).

#### `pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S>` [src]

Creates a raw immutable entry builder for the HashMap.

Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched.

This is useful for

- Hash memoization
- Using a search key that doesn’t work with the Borrow trait
- Using custom comparison logic without newtype wrappers

Unless you are in such a situation, higher-level and more foolproof APIs like `get` should be preferred.

Immutable raw entries have very limited use; you might instead want `raw_entry_mut`.

## Trait Implementations

### `impl<K: Clone, V: Clone, S: Clone> Clone for HashMap<K, V, S>` [src]

#### `fn clone(&self) -> Self` [src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)` [src]

Performs copy-assignment from `source`. Read more

### `impl<K, V, S> Debug for HashMap<K, V, S> where
K: Debug,
V: Debug,` [src]

#### `fn fmt(&self, f: &mut Formatter<'_>) -> Result` [src]

Formats the value using the given formatter. Read more

### `impl<K, V, S> Default for HashMap<K, V, S> where
S: Default,` [src]

#### `fn default() -> Self` [src]

Creates an empty `HashMap<K, V, S>`, with the `Default` value for the hasher.

### `impl<K, V, S> Eq for HashMap<K, V, S> where
K: Eq + Hash,
V: Eq,
S: BuildHasher,` [src]

### `impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S> where
K: Eq + Hash + Copy,
V: Copy,
S: BuildHasher,` [src]

#### `fn extend<T: IntoIterator<Item = (&'a K, &'a V)>>(&mut self, iter: T)` [src]

Extends a collection with the contents of an iterator. Read more

#### `pub fn extend_one(&mut self, item: A)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Extends a collection with exactly one element.

#### `pub fn extend_reserve(&mut self, additional: usize)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Reserves capacity in a collection for the given number of additional elements. Read more

### `impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S> where
K: Eq + Hash,
S: BuildHasher,` [src]

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

#### `fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T)` [src]

Extends a collection with the contents of an iterator. Read more

#### `pub fn extend_one(&mut self, item: A)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Extends a collection with exactly one element.

#### `pub fn extend_reserve(&mut self, additional: usize)` [src]

🔬 This is a nightly-only experimental API. (`extend_one`)

Reserves capacity in a collection for the given number of additional elements. Read more

### `impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S> where
K: Eq + Hash,
S: BuildHasher + Default,` [src]

#### `fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self` [src]

Creates a value from an iterator. Read more

### `impl<K, Q: ?Sized, V, S> Index<&'_ Q> for HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash,
S: BuildHasher,` [src]

#### `type Output = V`

The returned type after indexing.

#### `fn index(&self, key: &Q) -> &V` [src]

Returns a reference to the value corresponding to the supplied key.

# Panics

Panics if the key is not present in the `HashMap`.

### `impl<'a, K, V, S> IntoIterator for &'a HashMap<K, V, S>` [src]

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

#### `fn into_iter(self) -> Iter<'a, K, V>ⓘ

### Notable traits for Iter<'a, K, V>

`impl<'a, K, V> Iterator for Iter<'a, K, V> type Item = (&'a K, &'a V);`
` [src]

Creates an iterator from a value. Read more

### `impl<'a, K, V, S> IntoIterator for &'a mut HashMap<K, V, S>` [src]

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

#### `fn into_iter(self) -> IterMut<'a, K, V>ⓘ

### Notable traits for IterMut<'a, K, V>

`impl<'a, K, V> Iterator for IterMut<'a, K, V> type Item = (&'a K, &'a mut V);`
` [src]

Creates an iterator from a value. Read more

### `impl<K, V, S> IntoIterator for HashMap<K, V, S>` [src]

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

The type of the elements being iterated over.

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

Which kind of iterator are we turning this into?

#### `fn into_iter(self) -> IntoIter<K, V>ⓘ

### Notable traits for IntoIter<K, V>

`impl<K, V> Iterator for IntoIter<K, V> type Item = (K, V);`
` [src]

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();

### `impl<K, V, S> PartialEq<HashMap<K, V, S>> for HashMap<K, V, S> where
K: Eq + Hash,
V: PartialEq,
S: BuildHasher,` [src]

#### `fn eq(&self, other: &Self) -> bool` [src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `#[must_use]pub fn ne(&self, other: &Rhs) -> bool` 1.0.0 [src]

This method tests for `!=`.

## Auto Trait Implementations

### `impl<K, V, S> Send for HashMap<K, V, S> where
K: Send,
S: Send,
V: Send,`

### `impl<K, V, S> Sync for HashMap<K, V, S> where
K: Sync,
S: Sync,
V: Sync,`

### `impl<K, V, S> Unpin for HashMap<K, V, S> where
K: Unpin,
S: Unpin,
V: Unpin,`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `pub fn to_owned(&self) -> T` [src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `pub fn clone_into(&self, target: &mut T)` [src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into`)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.