Is it possible to hash a Swift protocol?

Question

I am trying to write a registry in Swift that maps from API's (Protocols) to Implementations (Classes). I would like to be able to provide the registry an API and receive back an instance of the class that implements it. In Objective-C this was fairly trivial - just call NSStringFromProtocol on the protocol and then use that as a key for a dictionary containing the classes that implement them. In Swift, however, we do not have this introspective capability. When I try to do the same I am told that MyAPI.protocol does not have a member "mirrorType". My question to you is how, in Swift, without using @objc protocols, I can map from a protocol itself to the class that implements it. Thanks!

Answer 1

By now it's not possible without using @objc. The solution I've found in this case is using the protocol name (string) as a key for the dictionary for this implementations (In my case I'll always have only one instance per Protocol).

Using @objc will force you to have all your implementations returning AnyObject the equivalent (id) in objective-C (if your function does not return a native objective-C type).

Hope that helps.