UILabel * label = [[UILabel alloc]initWithFrame:cell.bounds];
label.textAlignment = NSTextAlignmentLeft;
label.numberOfLines =0;
label.backgroundColor = [UIColor redColor];
label.text = [_dic objectForKey:@"course"];
//iOS 6.0如下
CGSize size = [label.text sizeWithFont:label.font constrainedToSize:CGSizeMake(self.view.frame.size.width, MAXFLOAT) lineBreakMode:NSLineBreakByWordWrapping];
label.frame = CGRectMake(label.frame.origin.x, label.frame.origin.y, size.width, size.height);
//iOS 7.0后如下
CGRect rect = [label.text boundingRectWithSize:CGSizeMake(self.view.frame.size.width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:label.font} context:nil];
label.frame = CGRectMake(label.frame.origin.x, label.frame.origin.y, rect.size.width, rect.size.height);
[cell addSubview:label];