iOS Label行距

调整label行距需要用label的attributedText属性，不需要用text属性了，如下：

        NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:newString];
        NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
        paragraphStyle.lineSpacing = 5; // 调整行间距
        NSRange range = NSMakeRange(0, [newString length]);
        [attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:range];
        self.detailLab.attributedText = attributedString;