UILabel设置下划线

    NSMutableAttributedString *content = [[NSMutableAttributedString alloc] initWithString:[NSString stringWithFormat:@"用户协议"]];

    NSRange contentRange = {0,[contentlength]};

    [content addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:contentRange];

    userAgreementLabel.attributedText =content;