iOS - 根据lable内容计算label高度

UILabel * lbl = [UILabel new];
lbl.font = [UIFont systemFontOfSize:18];
NSString *titleContent = @"a。";
lbl.text = titleContent;
lbl.numberOfLines = 0;
lbl.textColor = [UIColor lightGrayColor];

// 第一个参数是你约束label的大小,可以只约束宽度为50,则高度不做限制为最大浮点值
//第二个参数点进去固定写第一个属性
//第三个参数就是你设置label字体的大小的属性
//最后一个参数固定nil
//最后点. size即可
CGSize size = [titleContent boundingRectWithSize:CGSizeMake(50, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName : [UIFont systemFontOfSize:18]} context:nil].size;
CGFloat w = size.width;
CGFloat h = size.height;
CGFloat x = 0;
CGFloat y = 0;
lbl.frame = CGRectMake(x, y, w, h);
[self.view addSubview:lbl];
NSLog(@"%.2f---%.2f",w,h);
}

-(CGFloat)getLabelHeightWithContent:(NSString *)content andLabelWidth:(CGFloat)width andLabelFontSize:(int)font{

CGSize size = [content boundingRectWithSize:CGSizeMake(width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName : [UIFont systemFontOfSize:font]} context:nil].size;
return size.height;
}