UITextField占位文字颜色-attributedPlaceholder

如图，密码框是默认的占位文字的颜色，手机号是我们修改过后的。
代码如下：

// 占位文字属性    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];    attrs[NSForegroundColorAttributeName] = [UIColor whiteColor];    NSAttributedString *placeholder = [[NSAttributedString alloc] initWithString:@"手机号" attributes:attrs];    self.phoneField.attributedPlaceholder = placeholder;