Using addTarget(target:action:) without self - ios

Question

Is there any way to use addTarget on something other than self (which seems to be the most common use case)?

Answer 1

Yes, you can use a target other than self. The most common use is to call addTarget with self where self is a reference to the viewController that the adds the UIControl to its view hierarchy. But you aren't required to use it that way. The target is merely a reference to an object, so you can pass it a reference to any object you want. The action is a Selector which needs to be defined as an instance method on the class of that object, and that method must be available to Objective-C (marked with #objc or #IBAction) and it must take either no parameters, just the sender, or the sender and the event.
You can also pass nil as the target, which tells iOS to search up the responder chain for the action method.
Here's a little standalone example:
import UIKit
class Foo {
#objc func buttonClicked() {
print("clicked")
}
}
class ViewController: UIViewController {
let foo = Foo()
override func viewDidLoad() {
super.viewDidLoad()
let button = UIButton(frame: CGRect(x: 50, y: 200, width: 100, height: 30))
button.setTitle("Press me", for: .normal)
button.setTitleColor(.blue, for: .normal)
button.addTarget(foo, action: #selector(Foo.buttonClicked), for: .touchUpInside)
self.view.addSubview(button)
}
}

Answer 2

You can certainly set up some other object to receive control actions. Consider the following view controller:
First, define a class who's job is to respond to button tap actions:
#objc class ButtonTarget: NSObject {
#IBAction func buttonAction(_ sender: Any) {
print("In \(#function)")
}
}
Now define a view controller that creates a ButtonTarget object
class ViewController: UIViewController {
#IBOutlet weak var button: UIButton!
lazy var buttonTarget = ButtonTarget() //Give the ViewController a `ButtonTarget`
override func viewDidLoad() {
super.viewDidLoad()
//Add a taret/action to the button that invokes the method `buttonAction(_:)`
button.addTarget(
buttonTarget,
action: #selector(ButtonTarget.buttonAction(_:)),
for: .touchUpInside)
}
}