有时在使用 UILabel 时需要调整行间距，使用NSMutableAttributedString可以满足这一需求
UILabel *label = [[UILabel alloc] init];
label.font = Font(13);
label.numberOfLines = 0;
label.backgroundColor = [UIColor whiteColor];
label.textColor = LITTLE_TEXT_COLOR;
NSString *contentStr = @"内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀，内容够长才能换行呀";
NSMutableAttributedString *attContentStr = [[NSMutableAttributedString alloc] initWithString:contentStr];
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineSpacing:5];
[attContentStr addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [contentStr length])];
label.attributedText = attContentStr;
[label sizeToFit];
[scrollView addSubview:label];
[label mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(scrollView.mas_top).offset(15);
make.left.equalTo(scrollView.mas_left).offset(15);
make.width.mas_offset(SCREEN_WIDTH - 30);
}];
