iOS UILabel设置行间距

NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:unMember_lab.text];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineSpacing:8];
[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [unMember_lab.text length])];
unMember_lab.attributedText = attributedString;