Stuck with adding target to button programmatically - ios

Question

I've created a UIButton and I want it to print some message when it's pressed.
So I did something like this:
In loadView()
button.addTarget(self, action: #selector(ViewController.pressButton(button:)), for: .touchUpInside)
A method:
func pressButton(button: UIButton) {
NSLog("pressed!")
}
But nothing happens when I click the button.

Answer 1

Add the button code in your viewDidLoad and it will work for you:
override func viewDidLoad() {
super.viewDidLoad()
let button = UIButton(frame: CGRect(x: 10, y: 10, width: 100, height: 100))
button.backgroundColor = UIColor.gray
button.addTarget(self, action: #selector(pressButton(button:)), for: .touchUpInside)
self.view.addSubview(button)
}
func pressButton(button: UIButton) {
NSLog("pressed!")
}
You don´t need to add ViewController.pressButton to selector, it´s enough with the function name.
Swift 4.x version:
let button = UIButton(frame: CGRect(x: 10, y: 10, width: 100, height: 100))
button.backgroundColor = .gray
button.tag = 0
button.addTarget(self, action: #selector(pressButton(_:)), for: .touchUpInside)
self.view.addSubview(button)
#objc func pressButton(_ button: UIButton) {
print("Button with tag: \(button.tag) clicked!")
}
Swift 5.1 version:
let button = UIButton(frame: CGRect(x: 10, y: 10, width: 100, height: 100))
button.backgroundColor = .gray
button.tag = 100
button.addTarget(self, action: #selector(pressButton), for: .touchUpInside)
self.view.addSubview(button)
#objc func pressButton(button: UIButton) {
print("Button with tag: \(button.tag) clicked!")
}

Answer 2

try this in Swift3!
button.addTarget(self, action: #selector(self.pressButton(button:)), for: .touchUpInside)
#objc func pressButton(button: UIButton) { NSLog("pressed!") }

Answer 3

Use the following code.
button.addTarget(self, action: #selector(FirstViewController.cartButtonHandler), for: .touchUpInside)
Your class name corresponds to FirstViewController
And your selector corresponds to the following function
func cartButtonHandler() {
}

Answer 4

In swift 3 use this -
object?.addTarget(objectWhichHasMethod, action: #selector(classWhichHasMethod.yourMethod), for: someUIControlEvents)
For example(from my code) -
self.datePicker?.addTarget(self, action:#selector(InfoTableViewCell.datePickerValueChanged), for: .valueChanged)
Just give a : after method name if you want the sender as parameter.

Answer 5

You mention that the addTarget call is in loadView(). Is this in your custom subview, of some kind, or the viewController?
From your selector, it's targeting a method in your ViewController class, but if the target for this action is the view itself, then it would make sense that the action is not going through.
If you declare your button in a viewController, and in viewDidLoad add this target as above, then the message should be printed as you're looking for. I believe you are "targetting" the wrong class with your action.

Answer 6

let cancelButton = UIButton.init(frame: CGRect(x: popUpView.frame.size.width/2, y: popUpView.frame.size.height-20, width: 30, height: 30))
cancelButton.backgroundColor = UIColor.init(patternImage: UIImage(named: cancelImage)!)
cancelButton.addTarget(self, action: #selector(CommentsViewController.canceled), for:.touchUpInside)

Answer 7

Add the button code in override func viewDidLoad() method
Make sure your action handler tagged with #IBAction like this:
#IBAction func pressButton(button: UIButton) {
print("pressed!")
}
Then it will work!