动态适应label的高度

NSString *text = @"才能成为今年春晚才能从你去玩吧草桥结拜辞去调兵遣将吃不起吃不起维持年轻哦长宁区哦长宁区哦册起哦你且保持汽车拿起哦才弄器材齐全哦从前传播去传播企鹅翅膀去诶彼此企鹅并从企鹅传播企鹅出版企鹅哦吧从俄情报从鹅去传播企鹅次才能成为今年春晚才能从你去玩吧草桥结拜辞去调兵遣将吃不起吃不起维持年轻哦长宁区哦长宁区哦册起哦你且保持汽车拿起哦才弄器材齐全哦从前传播去传播企鹅翅膀去诶彼此企鹅并从企鹅传播企鹅出版企鹅哦吧从俄情报从鹅去传播企鹅次2";
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 40, 0, 0)];
label.backgroundColor=[UIColor grayColor];
label.font=[UIFont boldSystemFontOfSize:14];
[label setNumberOfLines:0];

label.text=text;
CGSize size=CGSizeMake(kScreenSize.width, MAXFLOAT);
CGSize labelsize = [text boundingRectWithSize:size options:NSStringDrawingUsesLineFragmentOrigin |NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:label.font} context:nil].size;
[label setFrame:CGRectMake(0, 40, labelsize.width, labelsize.height)];
[self.view addSubview:label];