iOS 修改UITextField的placeholder的颜色

//第一种  富文本

UIColor *color = [UIColor whiteColor];

_userName.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"用户名" attributes:@{NSForegroundColorAttributeName: color}];

//第二种  KVC 赋值

[_userName setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];