Can't set UIButton target in another class?

Question

I'm trying to build a custom controller to manage a set of UIButtons.

ViewController where buttons are setup and placed:

override func viewDidLoad() {
    super.viewDidLoad()

    let button1 = UIButton()
    button1.setTitle("Button 1", for: UIControlState.normal)
    button1.setTitleColor(UIColor.blue, for: UIControlState.normal)
    button1.frame.origin.y = 120
    button1.sizeToFit()
    button1.isUserInteractionEnabled = true

    let button2 = UIButton()
    button2.setTitle("Button 2", for: UIControlState.normal)
    button2.setTitleColor(UIColor.blue, for: UIControlState.normal)
    button2.frame.origin.y = 160
    button2.sizeToFit()


    let button3 = UIButton()
    button3.setTitle("Button 3", for: UIControlState.normal)
    button3.setTitleColor(UIColor.blue, for: UIControlState.normal)
    button3.frame.origin.y = 190
    button3.sizeToFit()

    let controller = CustomButtonController(buttons: button1, button2, button3)

    self.view.addSubview(button1)
    self.view.addSubview(button2)
    self.view.addSubview(button3) }

CustomButtonController:

class CustomButtonController : NSObject {
    init(buttons: UIButton...) {
        super.init()
        for aButton in buttons {
            aButton.addTarget(self, action: #selector(pressed(_:)), for: UIControlEvents.touchUpInside)
        }
    }

    func pressed(_ sender: UIButton) {
        print("Press received in CustomButtonController")
        //Never gets called
    }
}

If I use addTarget method on a button from inside the ViewController, then it works fine. Any idea why we can't add target to a passed UIButton like that? Thanks

Answer 1

You are creating your CustomButtonController as a local constant in viewDidLoad . As soon as viewDidLoad returns, this object is released and so is no longer around to handle the button taps.

You need to declare an instance property to hold the controller instance:

var controller: CustomButtonController!

override func viewDidLoad() {
    super.viewDidLoad()

    let button1 = UIButton()
    button1.setTitle("Button 1", for: UIControlState.normal)
    button1.setTitleColor(UIColor.blue, for: UIControlState.normal)
    button1.frame.origin.y = 120
    button1.sizeToFit()
    button1.isUserInteractionEnabled = true

    let button2 = UIButton()
    button2.setTitle("Button 2", for: UIControlState.normal)
    button2.setTitleColor(UIColor.blue, for: UIControlState.normal)
    button2.frame.origin.y = 160
    button2.sizeToFit()


    let button3 = UIButton()
    button3.setTitle("Button 3", for: UIControlState.normal)
    button3.setTitleColor(UIColor.blue, for: UIControlState.normal)
    button3.frame.origin.y = 190
    button3.sizeToFit()

    controller = CustomButtonController(buttons: button1, button2, button3)

    self.view.addSubview(button1)
    self.view.addSubview(button2)
    self.view.addSubview(button3) 
}