Swift add show action to button programmatically

  let button = UIButton(type: UIButtonType.Custom) as UIButton
  button.addTarget(self, action: "action:", forControlEvents: UIControlEvents.TouchUpInside)

  //then make a action method :

  func action(sender:UIButton!) {
     print("Button Clicked")
  }

You can go for below code
`

let btn: UIButton = UIButton(frame: CGRect(x: 100, y: 400, width: 100, height: 50))
btn.backgroundColor = UIColor.green
btn.setTitle("Click Me", for: .normal)
btn.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
btn.tag = 1
self.view.addSubview(btn) 

for action

 @objc func buttonAction(sender: UIButton!) {
        let btnsendtag: UIButton = sender
        if btnsendtag.tag == 1 {

            dismiss(animated: true, completion: nil)
        }
    }