Can I make #selector refer to a closure in Swift?

Question

I want to make a selector argument of my method refer to a closure property, both of them exist in the same scope. For example,

func backgroundC         


        

Answer 1

I tried this for UIBarButtonItem at least:

private var actionKey: Void?

extension UIBarButtonItem {

    private var _action: () -> () {
        get {
            return objc_getAssociatedObject(self, &actionKey) as! () -> ()
        }
        set {
            objc_setAssociatedObject(self, &actionKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }

    convenience init(title: String?, style: UIBarButtonItemStyle, action: @escaping () -> ()) {
        self.init(title: title, style: style, target: nil, action: #selector(pressed))
        self.target = self
        self._action = action
    }

    @objc private func pressed(sender: UIBarButtonItem) {
        _action()
    }

}

Then you can do this:

navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Test", style: .plain, action: {
    print("Hello World!")
})

Answer 2

Swift 5.2.x

First of all, you need to declare an "easy to use" typealias for your block:

typealias Completion = () -> ()

Then, you must declare private var to use "as a gate" for your function:

private var action: Completion?

After that, you should create a function that can be called by your Selector (it accept only string format) and to call private completion:

@objc func didAction() {
     self.action?()
}

Finally you can re-write your function (using the new swift syntax) like:

Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(didAction), userInfo: nil, repeats: false)
self.action = backToOriginalBackground

---

P.S.: Remember that your variable (or parameter if you embed it to a function) must be of the same of type declared to your typeAlias so, in our case:

var backToOriginalBackground: () -> ()

or also:

var backToOriginalBackground: Completion

Answer 3

No, #selector refers to an Objective-C method.

You can do something much better though: Add an extension to NSTimer that lets you create a scheduled timer not with a target and selector, but with a closure.

Answer 4

It is now possible. I've created a gist for block-based selectors in Swift 4.

https://gist.github.com/cprovatas/98ff940140c8744c4d1f3bcce7ba4543

Usage:

UIButton().addTarget(Selector, action: Selector { debugPrint("my code here") }, for: .touchUpInside)`

Answer 5

My solution was to create a class block variable like:

let completionBlock: () -> () = nil

Create a method which calls this completionBlock:

func completed(){
    self.completionBlock!()
}

And inside where I want to put my selector like a block I did:

func myFunc(){
  self.completionBlock = {//what I want to be done}
  NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, selector: #selector(Myclass.completed), userInfo: nil, repeats: false)
}