//设置全局变量,将下面的替换即可
    //var myTextField = UITextField();
    //系统生成的viewDidLoad()方法
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        //创建局部变量UITextField
        let myTextField = UITextField.init(frame: CGRectMake(20, 100, self.view.frame.width-40, 60));
        //设置文本
        //myTextField.text = "这是一个输入框";
        //设置占位符
        myTextField.placeholder = "请输入你的内容......";
        //设置字体大小
        myTextField.font = UIFont.systemFontOfSize(22);
        //设置编辑框右侧出现的删除图标
        myTextField.clearButtonMode = UITextFieldViewMode.WhileEditing;
        //设置边框大小，默认为0
        myTextField.layer.borderWidth = 2;
        //设置边框颜色，默认为黑色
        myTextField.layer.borderColor = UIColor.redColor().CGColor;
        //设置圆角
        myTextField.layer.cornerRadius = 8;
        //设置背景颜色
        myTextField.backgroundColor = UIColor.cyanColor();
        //设置是否安全显示
        //myTextField.secureTextEntry = true;
        //设置键盘样式
        //myTextField.keyboardType = UIKeyboardType.NumberPad;//纯数字类型
        
        //设置return键类型
        /*typedef enum {
         UIReturnKeyDefault, 默认 灰色按钮，标有Return
         UIReturnKeyGo,    　标有Go的蓝色按钮
         UIReturnKeyGoogle,标有Google的蓝色按钮，用语搜索
         UIReturnKeyJoin,标有Join的蓝色按钮
         UIReturnKeyNext,标有Next的蓝色按钮
         UIReturnKeyRoute,标有Route的蓝色按钮
         UIReturnKeySearch,标有Search的蓝色按钮
         UIReturnKeySend,标有Send的蓝色按钮
         UIReturnKeyYahoo,标有Yahoo的蓝色按钮
         UIReturnKeyYahoo,标有Yahoo的蓝色按钮
         UIReturnKeyEmergencyCall, 紧急呼叫按钮
         } UIReturnKeyType;*/
        myTextField.returnKeyType = UIReturnKeyType.Search;
        
        //添加左视图或右视图
        let leftImgView = UIImageView.init(frame: CGRectMake(0, 0, 60, 60));
        leftImgView.image = UIImage(named: "login_pwd.png");
        myTextField.leftView = leftImgView;
        //设置视图显示的方式,添加视图后必须写
        myTextField.leftViewMode = UITextFieldViewMode.Always;
        
        //设置代理
        myTextField.delegate = self;
        
        //添加视图
        self.view.addSubview(myTextField);
    }
    
    //UITextFieldDelegate
    func textFieldDidBeginEditing(textField: UITextField) {
        print("执行了开始编辑方法。。。。");
    }
    func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        print("执行了编辑框内容被某个值替换了的方法",string);
        return true;
    }