Swift 5和Swift 4一样

 let button = UIButton()
 button.frame = CGRect(x: self.view.frame.size.width - 60, y: 60, width: 50, height: 50)
 button.backgroundColor = UIColor.red
 button.setTitle("Name your Button ", for: .normal)
 button.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
 self.view.addSubview(button)

 @objc func buttonAction(sender: UIButton!) {
    print("Button tapped")
 }

将此代码添加到viewDidLoad中 / /添加按钮

            var button=UIButton(frame: CGRectMake(150, 240, 75, 30))
            button.setTitle("Next", forState: UIControlState.Normal)
            button.addTarget(self, action: "buttonTapAction:", forControlEvents: UIControlEvents.TouchUpInside)
            button.backgroundColor = UIColor.greenColor()
            self.view.addSubview(button)

将这个函数写在它的外面，当你点击按钮时，这个函数将被调用

func buttonTapAction(sender:UIButton!)
{
    println("Button is working")
}

你可以通过这种方式添加UIButton,UIlable和UITextfield。

UIButton代码

// var button   = UIButton.buttonWithType(UIButtonType.System) as UIButton
let button = UIButton(type: .System) // let preferred over var here
button.frame = CGRectMake(100, 100, 100, 50)
button.backgroundColor = UIColor.greenColor()
button.setTitle("Button", forState: UIControlState.Normal)
button.addTarget(self, action: "Action:", forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(button)

UILabel代码

var label: UILabel = UILabel()
label.frame = CGRectMake(50, 50, 200, 21)
label.backgroundColor = UIColor.blackColor()
label.textColor = UIColor.whiteColor()
label.textAlignment = NSTextAlignment.Center
label.text = "test label"
self.view.addSubview(label)

UITextField 代码

var txtField: UITextField = UITextField()
txtField.frame = CGRectMake(50, 70, 200, 30)
txtField.backgroundColor = UIColor.grayColor()
self.view.addSubview(txtField)

希望这对你有帮助。

Swift 3

let button = UIButton()
button.frame = CGRect(x: self.view.frame.size.width - 60, y: 60, width: 50, height: 50)
button.backgroundColor = UIColor.red
button.setTitle("your Button Name", for: .normal)
button.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
self.view.addSubview(button)

func buttonAction(sender: UIButton!) {
    print("Button tapped")
}

Swift 4+

 let button = UIButton()
 button.frame = CGRect(x: self.view.frame.size.width - 60, y: 60, width: 50, height: 50)
 button.backgroundColor = UIColor.red
 button.setTitle("Name your Button ", for: .normal)
 button.addTarget(self, action: #selector(buttonAction), for: .touchUpInside)
 self.view.addSubview(button)

 @objc func buttonAction(sender: UIButton!) {
    print("Button tapped")
 }

Uilabel code 

var label: UILabel = UILabel()
label.frame = CGRectMake(50, 50, 200, 21)
label.backgroundColor = UIColor.blackColor()
label.textColor = UIColor.whiteColor()
label.textAlignment = NSTextAlignment.Center
label.text = "test label"
self.view.addSubview(label)

 func viewDidLoad(){
                    saveActionButton = UIButton(frame: CGRect(x: self.view.frame.size.width - 60, y: 0, width: 50, height: 50))
                    self.saveActionButton.backgroundColor = UIColor(red: 76/255, green: 217/255, blue: 100/255, alpha: 0.7)
                    saveActionButton.addTarget(self, action: #selector(doneAction), for: .touchUpInside)
                    self.saveActionButton.setTitle("Done", for: .normal)
                    self.saveActionButton.layer.cornerRadius = self.saveActionButton.frame.size.width / 2
                    self.saveActionButton.layer.borderColor = UIColor.darkGray.cgColor
                    self.saveActionButton.layer.borderWidth = 1
                    self.saveActionButton.center.y = self.view.frame.size.height - 80
                    self.view.addSubview(saveActionButton)
        }

          func doneAction(){
          print("Write your own logic")
         }