Trait objc2::mutability::HasStableHash

pub unsafe trait HasStableHash: Sealed { }

Marker trait for classes whose hash and isEqual: methods are stable.

This is useful for hashing collection types like NSDictionary and NSSet which require that their keys never change.

This is implemented for classes whose ClassType::Mutability is one of:

• Immutable.
• Mutable.
• ImmutableWithMutableSubclass.
• MutableWithImmutableSuperclass.

Since all of these do not use interior mutability, and since the hash and isEqual: methods are required to not use external sources like thread locals or randomness to determine their result, we can guarantee that the hash is stable for these types.

Safety

This is a sealed trait, and should not need to be implemented. Open an issue if you know a use-case where this restrition should be lifted!

Implementors

impl<P: ?Sized + HasStableHash> HasStableHash for ProtocolObject<P>

impl<T: ?Sized + ClassType> HasStableHash for T

where T::Mutability: MutabilityHashIsStable,