iOS Label 自适应高度 适配iOS7以后的版本
self.contentLabelView = [[UILabel alloc] init];
self.contentLabelView.font = SYS_FONT(15);
self.contentLabelView.lineBreakMode =NSLineBreakByTruncatingTail ;
self.contentLabelView.textColor = [UIColor colorWithHexString:@"#444444"];
self.contentLabelView.text =[@"12312312312312321321dddsdadsadasdasdas" stringByAppendingString:@"\n\n\n\n\n\n\n"];
[self.contentLabelView setNumberOfLines:0];
//根据内容计算出label所需要的高度
CGSize size = CGSizeMake(kScreenWidth - expectSizes.width-20, MAXFLOAT);
NSDictionary * tdic = [NSDictionary dictionaryWithObjectsAndKeys:self.contentLabelView.font,NSFontAttributeName,nil];
CGSize actualsize =[self.contentLabelView.text boundingRectWithSize:size options:NSStringDrawingUsesLineFragmentOrigin attributes:tdic context:nil].size;
self.contentLabelView.frame =CGRectMake(expectSizes.width+20, 254, actualsize.width, actualsize.height);
纯代码布局可能会用到，不过推荐使用xib或storyboard。