Swift -- Require classes implementing protocol to be subclasses of a certain class
Update. In the latest Swift version you can just write
protocol TransmogrifiableView: NSView { func transmogrify()}, and this will enforce the conformer types to be either NSView, or a subclass of it. This means the compiler will "see" all members of NSView.
Original answer
There is a workaround by using associated types to enforce the subclass:
protocol TransmogrifiableView { associatedtype View: NSView = Self func transmogrify()}class MyView: NSView, TransmogrifiableView { ... } // compilesclass MyOtherClass: TransmogrifiableView { ... } // doesn't compile
Starting from Swift 4 you can now define this as followed:
let myView: NSView & TransmogrifiableViewFor more information, checkout issue #156 Subclass Existentials
You could use something like this:
protocol TransmogrifiableView where Self:NSView {}This requires all created instances which one conforms to TransmogrifiableView protocol to be subclassed with NSView