Struct HashMap

pub struct HashMap<K, S>(/* private fields */);

Polymorphic hash map

Internally this uses a HashMap with boxed values, thus performance is much like that of HashMap.

Note: HashMap’s capacity reservation API is excluded. There is no fundamental reason for this, other than each stored value requiring an allocation (boxing) anyway.

Warning

Warning: values stored in the map will not have their destructor (Drop::drop) run when the map is destroyed. This is not currently fixable (min_specialization + https://github.com/rust-lang/rust/issues/46893 may be sufficient).

Implementations

impl<K> HashMap<K, RandomState>

pub fn new() -> Self

Construct a new store

impl<K, S> HashMap<K, S>

pub fn with_hasher(hash_builder: S) -> Self

Construct a new store with the given hash bulider

pub fn hasher(&self) -> &S

Return’s a reference to the map’s BuildHasher

pub fn keys(&self) -> Keys<'_, K, Box<dyn Any>>

Returns an iterator over all keys in arbitrary order

These are not tagged keys; only the bare key is stored.

pub fn len(&self) -> usize

Returns the number of elements in the store

pub fn is_empty(&self) -> bool

Returns true if the store contains no elements

pub fn clear(&mut self)

Clears the store, removing all elements

impl<K: Eq + Hash, S: BuildHasher> HashMap<K, S>

pub fn contains_key(&self, key: &K) -> bool

Checks whether a value matching the specified key exists

pub fn get_type_id(&self, key: &K) -> Option<TypeId>

Get the TypeId of a stored value

pub fn get_tagged<V: 'static>(&self, key: &TaggedKey<K, V>) -> Option<&V>

Returns a reference to the value corresponding to the key

The value’s type is inferred from the TaggedKey.

Returns None if no element matches tag or if the type V does not match the element.

pub fn get<V: 'static>(&self, key: &K) -> Option<&V>

Returns a reference to the value corresponding to the key

The value’s type must be specified explicitly.

Returns None if no element matches key. Panics on type mismatch.

pub fn get_tagged_mut<V: 'static>( &mut self, key: &TaggedKey<K, V>, ) -> Option<&mut V>

Returns a mutable reference to the value corresponding to the key

pub fn get_mut<V: 'static>(&mut self, key: &K) -> Option<&mut V>

Returns a mutable reference to the value corresponding to the key

Returns None if no element matches key. Panics on type mismatch.

pub fn insert<V: 'static>(&mut self, key: K, value: V) -> TaggedKey<K, V>

where K: Clone,

Inserts a key-value pair into the store

Returns the corresponding TaggedKey for convenience.

Unlike HashMap this does not return any displaced old value since the type of any such value is unknown.

pub fn insert_boxed<V: 'static>( &mut self, key: K, value: Box<V>, ) -> TaggedKey<K, V>

where K: Clone,

Inserts a key and boxed value pair

Returns the corresponding TaggedKey for convenience.

Unlike HashMap this does not return any displaced old value since the type of any such value is unknown.

pub fn remove<V: 'static>(&mut self, key: &TaggedKey<K, V>) -> Option<V>

Removes and returns a value, if present

Panics on type mismatch.

pub fn remove_boxed<V: 'static>( &mut self, key: &TaggedKey<K, V>, ) -> Option<Box<V>>

Removes and returns a value, if present

Panics on type mismatch.

pub fn entry<V: 'static>(&mut self, key: K) -> Entry<'_, K, V>

Get key’s entry for in-place manipulation

Trait Implementations

impl<K: Debug, S: Debug> Debug for HashMap<K, S>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<K, S: Default> Default for HashMap<K, S>

fn default() -> Self

Returns the “default value” for a type.