Struct Key

pub struct Key<V> { /* private fields */ }

A type-safe key used to fetch values from the value store.

Construction

A key can be constructed only by calling State::insert. The state assigns a new numerical ID to the inserted value, which is unique throughout the running of the program. This ensures type safety, as explained below.

Type Safety

These keys are type-safe in a sense that a key used to insert a value of type T cannot be used to access a value of another type U. An attempt to do so will result in a compile error. It is achieved by having the key generic over T. However, T is just a marker, and no values of type T are stored internally.

let mut state = State::default();
let id = state.insert(String::from("1"));
let _: Option<i32> = state.remove(id);  // Error!
let _ = state.remove::<i32>(id);        // Error!

Trait Implementations

impl<T> Clone for Key<T>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<V: Debug> Debug for Key<V>

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

Formats the value using the given formatter.

impl<V: Hash> Hash for Key<V>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<V: PartialEq> PartialEq for Key<V>

fn eq(&self, other: &Key<V>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T> Copy for Key<T>

impl<V: Eq> Eq for Key<V>

impl<V> StructuralPartialEq for Key<V>