代码（XIB）实现UIButton、UILabel文字添加下划线小技巧

UILabel设置下划线:

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 100, 310, 50)];
label.backgroundColor = [UIColor redColor];
[label setLineBreakMode:NSLineBreakByWordWrapping];
label.numberOfLines =3;
[label setFont:[UIFont systemFontOfSize:14]];
NSMutableAttributedString *slfstring = [[NSMutableAttributedString alloc]initWithString:
[NSString stringWithFormat:@"其他精彩博文http://blog.csdn.net/s651836663"]];
NSRange slfstringRange = {0,[slfstring length]};
[slfstring addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle]
 range:slfstringRange];

label.attributedText = slfstring;
[self.view addSubview:label];

UIButton设置下划线:

UIButton *button=[[UIButton alloc]initWithFrame:CGRectMake(10, 200, 80, 30)];
  NSMutableAttributedString *title = [[NSMutableAttributedString alloc] initWithString:
@"其他精彩博文http://blog.csdn.net/s651836663"];
  NSRange titleRange = {0,[title length]};
  [title addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle]
 range:titleRange];
  [button setAttributedTitle:title
                    forState:UIControlStateNormal];
  [button setBackgroundColor:[UIColor redColor]];
  [button.titleLabel setFont:[UIFont systemFontOfSize:14]];
  [self.view addSubview:button];

如果有些童鞋是通过XIB来实现label和button的也不用着急，将上述代码中的label和button的创建删除，换成你在XIB中
创建的对象 名 即可

改变下划线颜色：

[title addAttribute:NSUnderlineColorAttributeName value:[UIColor grayColor] range:(NSRange){0,[title length]}];

下划线样式：

NSUnderlineStyleNone = 0x00, 无下划线

NSUnderlineStyleSingle = 0x01, 单行下划线

NSUnderlineStyleThick NS_ENUM_AVAILABLE(10_0, 7_0) = 0x02, 粗的下划线

NSUnderlineStyleDouble NS_ENUM_AVAILABLE(10_0, 7_0) = 0x09, 双下划线