Alternative to performSelector in Swift?

Question

The performSelector family of methods are not available in Swift. So how can you call a method on an @objc object, where the method to be called is chosen at runtime, and not known at compile time? NSInvocation is apparently also not available in Swift.

I know that in Swift, you can send any method (for which there is an @objc method declaration visible) to the type AnyObject, similar to id in Objective-C. However, that still requires you to hard-code the method name at compile-time. Is there a way to dynamically choose it at runtime?

Answer 1

Using closures

class A {
    var selectorClosure: (() -> Void)?

    func invoke() {
        self.selectorClosure?()
    }
}

var a = A()
a.selectorClosure = { println("Selector called") }
a.invoke()

Note that this is nothing new, even in Obj-C the new APIs prefer using blocks over performSelector (compare UIAlertView which uses respondsToSelector: and performSelector: to call delegate methods, with the new UIAlertController).

Using performSelector: is always unsafe and doesn't play well with ARC (hence the ARC warnings for performSelector:).