IOS(Swift)重写一个带占位符的textView

class PlaceStrTextView: UIView,UITextViewDelegate{
    
    var palceStr = "即将输入的信息" //站位文字
    var inputStr = "" //输入的信息
    
    //创建一个textView
    lazy var textView:UITextView = {
        let tv = UITextView()
        tv.delegate = self
        tv.text = self.palceStr
        tv.textColor = UIColor.gray
        tv.backgroundColor = UIColor.clear
        tv.font = UIFont.systemFont(ofSize: 15)
        return tv
    }()
    
    //私有方法
    func overrideSelf(frame: CGRect) {
        self.frame = frame
        addTextView()
    }
    
    //添加textView
    func addTextView(){
        self.textView.frame = CGRect(x: 0, y: 0, width: self.frame.width, height: self.frame.height)
        self.addSubview(self.textView)
    }
    
    func textViewDidBeginEditing(_ textView: UITextView) {
        if textView.text == palceStr { //一旦开始编辑就将textView滞空并将颜色改为黑色
            textView.text = ""
        }
        textView.textColor = UIColor.black
    }
    
    func textViewDidEndEditing(_ textView: UITextView) {
        if textView.text == "" {//如果用户没有输入任何信息就显示站位字符串
            textView.text = palceStr
            textView.textColor = UIColor.gray
        }else{//一旦输入了信息你则颜色变成黑色
            textView.textColor = UIColor.black
        }
    }
    
    func hiddenKeyBoard(){
        (UIApplication.shared.delegate as! AppDelegate).window?.rootViewController?.view.endEditing(true)
        inputStr = textView.text
    }
    
}

     //调用示例
     @IBOutlet weak var textView: PlaceStrTextView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        textView.palceStr = "埃及的妇女节阿萨德来看风景安东尼设计开发"
        textView.overrideSelf(frame: textView.frame)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func tapAction(_ sender: Any) {
        textView.hiddenKeyBoard()
        print(textView.inputStr)
    }