ios13 foeKeyPath不允许访问私有变量 崩溃 _placeholderLabel

下方代码在ios13 中会崩溃

//[ self.contentTextField setValue:KRGBColor(154, 154, 154, 1.0) forKeyPath:@"_placeholderLabel.textColor"];
//[ self.contentTextField setValue:[UIFont systemFontOfSize:13.0] forKeyPath:@"_placeholderLabel.font"];
//UITextField *textfield = [[UITextField alloc]init];

调整方法，通过attributedPlaceholder属性

NSMutableAttributedString *arrStr = [[NSMutableAttributedString alloc]initWithString:self.contentTextField.placeholder attributes:@{NSForegroundColorAttributeName : KRGBColor(154, 154, 154, 1.0),NSFontAttributeName:[UIFont systemFontOfSize:13.0]}];
self.contentTextField.attributedPlaceholder = arrStr;