CODEWITHSUNDEEP
iosswift
ssrobbi
ssrobbi

Reputation: 571

How to use dynamic types conforming to protocols

I'm just trying to get a grasp as to why this isn't possible. Why can I not use a dynamic type with this setup. (I put this in playgrounds):

protocol SomeProtocol {
    init()
}

class SomeClass : SomeProtocol {
    required init() { }
}

let x: SomeProtocol.Type = SomeClass.self

x()

When this runs, playgrounds will crash, and if you try to put code like this in Xcode it will throw a

Command failed due to signal: Segmentation fault: 11

If I, however, never call x(), I can print out x to be of the correct SomeClass.Type.

I realize this is a weird setup, so I understand the confusion of "why would you ever want to do that?". But that aside; is it possible? not possible? Is it a bug? Am I not understanding how protocols really work?

Upvotes: 0

Views: 89

Answers (1)

matt
matt

Reputation: 534949

It works fine. I tried your code in Xcode 7 and it compiles and runs. Of course, in real code you can't say x() at top level. And in Swift 2 you have to say x.init(), not x(). But when you do, it's fine.

protocol SomeProtocol {
    init()
}
class SomeClass : SomeProtocol {
    required init() { }
}
class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let x: SomeProtocol.Type = SomeClass.self
        x.init()
    }
}

Upvotes: 1

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