iOS开发修改UITextField的placeholder的颜

贴上代码

UITextField *textField = [UITextField new];
NSString *placeHolderStr = @"我是placeholder";
textField.placeholder = placeHolderStr;
NSMutableAttributedString *placeholder = [[NSMutableAttributedString alloc] initWithString:placeHolderStr];
[placeholder addAttribute:NSForegroundColorAttributeName
                        value:[UIColor whiteColor]
                        range:NSMakeRange(0, placeHolderStr.length)];
[placeholder addAttribute:NSFontAttributeName
                        value:[UIFont boldSystemFontOfSize:16]
                        range:NSMakeRange(0, placeHolderStr.length)];
textField.attributedPlaceholder = placeholder;