pub unsafe trait Key:
From<KeyData>
+ Copy
+ Clone
+ Default
+ Eq
+ PartialEq
+ Ord
+ PartialOrd
+ Hash
+ Debug {
// Required method
fn data(&self) -> KeyData;
// Provided methods
fn null() -> Self { ... }
fn is_null(&self) -> bool { ... }
}
Expand description
Key used to access stored values in a slot map.
Do not use a key from one slot map in another. The behavior is safe but non-sensical (and might panic in case of out-of-bounds).
To prevent this, it is suggested to have a unique key type for each slot
map. You can create new key types using new_key_type!
, which makes a
new type identical to DefaultKey
, just with a different name.
This trait is intended to be a thin wrapper around KeyData
, and all
methods must behave exactly as if we’re operating on a KeyData
directly.
The internal unsafe code relies on this, therefore this trait is unsafe
to
implement. It is strongly suggested to simply use new_key_type!
instead
of implementing this trait yourself.
Required Methods§
Provided Methods§
sourcefn null() -> Self
fn null() -> Self
Creates a new key that is always invalid and distinct from any non-null
key. A null key can only be created through this method (or default
initialization of keys made with new_key_type!
, which calls this
method).
A null key is always invalid, but an invalid key (that is, a key that has been removed from the slot map) does not become a null key. A null is safe to use with any safe method of any slot map instance.
§Examples
let mut sm = SlotMap::new();
let k = sm.insert(42);
let nk = DefaultKey::null();
assert!(nk.is_null());
assert!(k != nk);
assert_eq!(sm.get(nk), None);