iOS textView 的 placeholder、字数限制、行数限制最优雅的解决方式

 //    textView.font = [UIFont systemFontOfSize:17];
//    textView.text = @"请�写在自定义属性前面，如果长度大于limitLength设置长度会被自动截断。";
  textView.placeholder = @"欢迎";
  textView.limitLength = @20;
  textView.placeholdColor = [UIColor redColor];
  textView.limitPlaceColor = [UIColor redColor];
  textView.placeholdFont = [UIFont systemFontOfSize:17];
  textView.limitPlaceFont = [UIFont systemFontOfSize:17];
  //    textView.limitLines = @4;//行数限制优先级低于字数限制
  [self.view addSubview:textView];

        let textview = UITextView(frame: CGRect(x: 100, y: 100, width: 200, height: 150))
//        textview.text = "如果你想对textView.text直接赋值。请在设置属性之前进行，否则影响计算"
        textview.placeholder = "喜欢请Star"
        textview.limitLength = 20
        textview.placeholdColor = .red
        textview.limitLabelColor = .red
        textview.placeholdFont = UIFont.boldSystemFont(ofSize: 17)
        textview.limitLabelFont = UIFont.boldSystemFont(ofSize: 17)
//        textview.limitLines = 4;
        textview.center = self.view.center
        view.addSubview(textview)