iOS UILabel自适应宽度

UILabel * label = [[UILabel alloc]initWithFrame:CGRectMake(100, 100, 80, 20)];

    label.backgroundColor = [UIColor whiteColor];

    label.textColor = [UIColor blackColor];

    label.text = @"很久很久查询";

    label.textAlignment = NSTextAlignmentCenter;

    codeLabel.font = [UIFont systemFontOfSize:12];

    [self.view addSubview:codeLabel];

//第一种方法

            CGSize size = [label.text sizeWithFont:label.font constrainedToSize:CGSizeMake(300, label.frame.size.height)];

//第二种方法

            CGSize size = [label.text boundingRectWithSize:CGSizeMake(300, label.frame.size.height) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:label.font} context:nil].size;