Swift UI

class ViewController: UIViewController {
var label : UILabel?

var textField : UITextField?
override func viewDidLoad() {
super.viewDidLoad()
label = UILabel(frame: CGRect(x: 0, y: 0, width: 300, height: 30))
label?.center = CGPoint(x: CGRectGetMidX(self.view.bounds) ,y: 200)
label?.text = "Hello World"
label?.textAlignment = NSTextAlignment.Center
label?.textColor = UIColor.redColor()
label?.font = UIFont.systemFontOfSize(20)
self.view.addSubview(label!)


textField = UITextField(frame: CGRect(x: 200, y: 300, width: 300, height: 30))
textField?.borderStyle = .RoundedRect
self.view.addSubview(textField!)


let button = UIButton(type: .System)
button.frame = CGRect(x: 0, y: 0, width: 300, height: 30)
button.center = CGPoint(x: CGRectGetMidX(self.view.bounds), y: 400)
button.backgroundColor = UIColor.redColor()
button.setTitleColor(UIColor.blackColor(), forState: UIControlState.Normal)
button.setTitle("确定", forState: UIControlState.Normal)

button.addTarget(self, action: "buttonPressed:", forControlEvents: UIControlEvents.TouchUpInside)
self.view.addSubview(button)
}

func buttonPressed(sender:UIButton){
label?.text = textField?.text
}