iOS 文字下划线

1  NSMutableAttributedString *content = [[NSMutableAttributedString alloc]initWithString:text];
2     NSRange contentRange = {0,[content length]};
3     [content addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:contentRange];
4     
5     [_titleLabel setAttributedText:content];