iOS Swift How to create a Protocol instance

Question

I am a Android developer, and I'm very new to Swift so please bear with me. I am trying to implement callback functions with Protocol in Swift. In Java I can create an Interface and make it an instance without linking it to any implementing class so that I can pass it around, for example:

public interface SomeListener {
    void done(); 
}

SomeListener listener = new SomeListener() {
    @Override
    public void done() {
        // do something
    }
}
listener.done();

How can I do it with Protocol in Swift? Or can it actually be done?

No it can't be done. You need a concrete implementation class or struct. — Antonio
– Antonio, Commented Dec 23, 2014 at 9:02
This might help you : developer.apple.com/library/ios/documentation/Swift/Conceptual/… — Yuyutsu
– Yuyutsu, Commented Dec 23, 2014 at 9:42

HorseT · Accepted Answer · 2014-12-23 09:36:41Z

13

That`s a way you can implement a protocol. Its like the delegate pattern in ObjC

protocol DoneProtocol {
    func done()
}

class SomeClass {
    var delegate:DoneProtocol?

    func someFunction() {
        let a = 5 + 3
        delegate?.done()
    }
}

class Listener : DoneProtocol {
   let someClass = SomeClass()

   init() {
       someClass.delegate = self
       someClass.someFunction()
   }
   // will be called after someFunction() is ready
   func done() {
       println("Done")
   }
}

answered Dec 23, 2014 at 9:36

HorseT

6,5922 gold badges20 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Guster Over a year ago

Just did some research, so apparently Swift doesn't have an anonymous class behavior yet, i guess this is the only way, thanks!

David Berry Over a year ago

@gricher Java uses anonymous classes primarily as a way around the fact that the language doesn't support closures (think inline anonymous functions) Since Swift does support closures there is much less need for anonymous classes, and the syntax winds up being much cleaner besides.

Collectives™ on Stack Overflow

iOS Swift How to create a Protocol instance

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related