Identifiable

Use the Identifiable protocol to provide a stable notion of identity to a class or value type. For example, you could define a User type with an id property that is stable across your app and your app’s database storage. You could use the id property to identify a particular user even if other data fields change, such as the user’s name.

Identifiable leaves the duration and scope of the identity unspecified. Identities can have any of the following characteristics:

• Guaranteed always unique, like UUIDs.

• Persistently unique per environment, like database record keys.

• Unique for the lifetime of a process, like global incrementing integers.

• Unique for the lifetime of an object, like object identifiers.

• Unique within the current collection, like collection indices.

It’s up to both the conformer and the receiver of the protocol to document the nature of the identity.

Conforming to the Identifiable Protocol

Identifiable provides a default implementation for class types (using ObjectIdentifier), which is only guaranteed to remain unique for the lifetime of an object. If an object has a stronger notion of identity, it may be appropriate to provide a custom implementation.