UITextField

override func viewDidLoad() {
        super.viewDidLoad()
        
        let textField = UITextField(frame: CGRect(x: 20.0, y: 60.0, width: 200.0, height: 30.0))
        textField.borderStyle = UITextField.BorderStyle.roundedRect
        textField.placeholder = "请输入...."
        textField.adjustsFontSizeToFitWidth = true
        textField.minimumFontSize = 10.0
        self.view.addSubview(textField)
        
        textField.returnKeyType = .join
        textField.delegate = self
        textField.clearButtonMode = .whileEditing    
    }

func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        
        NSLog("textField - %@", textField.text!)
        NSLog("textFieldShouldReturn")
        return true
    }