修改UITextfield的Placeholder字体的颜色

//第一种   UIColor *color = [UIColor whiteColor];    _userName.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"用户名" attributes:@{NSForegroundColorAttributeName: color}];//第二种 [_userName setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];