Struct Attributes

Source

pub struct Attributes(/* private fields */);

Methods from Deref<Target = HashMap<AttrValue, AttrValue>>§

1.0.0 · Source

pub fn capacity(&self) -> usize

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

1.0.0 · Source

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

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

§Examples

use std::collections::HashMap;

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

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

§Performance

In the current implementation, iterating over keys takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

1.0.0 · Source

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

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

§Examples

use std::collections::HashMap;

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

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

§Performance

In the current implementation, iterating over values takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

1.0.0 · Source

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

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

§Examples

use std::collections::HashMap;

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

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

§Performance

In the current implementation, iterating over map takes O(capacity) time instead of O(len) because it internally visits empty buckets too.

1.0.0 · Source

pub fn len(&self) -> usize

Returns the number of elements in the map.

§Examples

use std::collections::HashMap;

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

1.0.0 · Source

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

§Examples

use std::collections::HashMap;

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

1.9.0 · Source

pub fn hasher(&self) -> &S

Returns a reference to the map’s BuildHasher.

§Examples

use std::collections::HashMap;
use std::hash::RandomState;

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

1.0.0 · Source

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

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 std::collections::HashMap;

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

1.40.0 · Source

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

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 std::collections::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);

1.0.0 · Source

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

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 std::collections::HashMap;

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

Source

pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S>

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

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