How do I specify that a non-generic Swift type should comply to a protocol?

Question

I\'d like to implement a Swift method that takes in a certain class type, but only takes instances of those classes that comply to a specific protocol. For example, in Objec

Answer 1

this method header from ObjC:

- (void)addFilter:(GPUImageOutput *)newFilter { ... }

is identical to this header in Swift:

func addFilter(newFilter: T?) { ... }

both method will accept the same set of classes

• which is based on GPUImageOutput class; and
• conforms GPUImageInput protocol; and
• the newFilter is optional, it can be nil;