IOS13后更改textField占位字的颜色

/* IOS13之后这个方法更改颜色会引起app奔溃，所以需要用后面两种方法代替
[self.searchTF setValue:[UIColor whiteColor]    forKeyPath:@"_placeholderLabel.textColor"];

**/

/* IOS 13后需要用下面的方法
     NSMutableDictionary * dict = [NSMutableDictionary dictionary];
     dict[NSForegroundColorAttributeName] = [UIColor whiteColor];
     
     NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:self.placeholder attributes:dict];
     self.attributedPlaceholder = attrStr;
     **/
    

/*或者用这个方法
 Ivar ivar =  class_getInstanceVariable([UITextField class], "_placeholderLabel");
UILabel *placeholderLabel = object_getIvar(self.searchTF, ivar);
placeholderLabel.textColor = [UIColor whiteColor];
 **/