How to create a UIButton programmatically - swift

Question

I am trying to build UIViews programmatically. How do I get a UIButton with an action function in Swift?
The following code does not get any action:
let btn: UIButton = UIButton(frame: CGRectMake(100, 400, 100, 50))
btn.backgroundColor = UIColor.greenColor()
btn.setTitle("Click Me", forState: UIControlState.Normal)
btn.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(buttonPuzzle)
The following selector function is:
func buttonAction(sender: UIButton!) {
var btnsendtag: UIButton = sender
}

Answer 1

You're just missing which UIButton this is. To compensate for this, change its tag property.
Here is you answer:
let btn: UIButton = UIButton(frame: CGRectMake(100, 400, 100, 50))
btn.backgroundColor = UIColor.greenColor()
btn.setTitle("Click Me", forState: UIControlState.Normal)
btn.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)
btn.tag = 1 // change tag property
self.view.addSubview(btn) // add to view as subview
Swift 3.0
let btn: UIButton = UIButton(frame: CGRect(x: 100, y: 400, width: 100, height: 50))
btn.backgroundColor = UIColor.green
btn.setTitle(title: "Click Me", for: .normal)
btn.addTarget(self, action: #selector(buttonAction), forControlEvents: .touchUpInside)
btn.tag = 1
self.view.addSubview(btn)
Here is an example selector function:
func buttonAction(sender: UIButton!) {
var btnsendtag: UIButton = sender
if btnsendtag.tag == 1 {
//do anything here
}
}

Answer 2

Using a tag is a fragile solution. You have a view and you are creating and adding the button to that view, you just need to keep a reference to it: For example
In your class, keep a reference to the button
var customButton: UIButton!
Create the button and set the reference
let btn = UIButton(frame: CGRect(x: 100, y: 400, width: 100, height: 50))
btn.backgroundColor = .greenColor()
btn.setTitle("Click Me", forState: .Normal)
btn.addTarget(self, action: #selector(MyClass.buttonAction), forControlEvents: .TouchUpInside)
self.view.addSubview(btn)
customButton = btn
Test against this instance in the action function
func buttonAction(sender: UIButton!) {
guard sender == customButton else { return }
// Do anything you actually want to do here
}

Answer 3

You have to addSubview and tag on that btn.