UILabel 根据text的内容来调整大小

//文字的字体
NSDictionary *attribute = @{NSFontAttributeName:[UIFont fontWithName:@"Heiti SC" size:15.0f]};

 
//将text转化为NSMutableAttributedString类型
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:_titleLabel.text attributes:attribute];
 
//设置行间距
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineSpacing:6.0f];
[attributedString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [_titleLabel.text length])];
 
//获得UILabel的size，其中，296和93是size的限定值
CGSize DateSize = [attributedString boundingRectWithSize:CGSizeMake(296, 93) options: NSStringDrawingTruncatesLastVisibleLine | NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading  context:nil].size;
    
//如果UILabel的宽度太宽的话
if (DateSize.width > 518.0f/2) 
{ 
    _titleLabel.size = CGSizeMake(296.0f, DateSize.height);
    _titleLabel.textAlignment = NSTextAlignmentLeft;
    _titleLabel.lineBreakMode = NSLineBreakByCharWrapping;
    _titleLabel.numberOfLines = 0;  //不限定行数，自动换行
    _titleLabel.attributedText = attributedString;
}