UILabel的高度（height）自适应文字内容(text)

方法一

首先计算出字符串在已知宽度的View中的size，然后改变View的size就可以。

示例代码如下：

#define IOS7_OR_LATER   ( [[[UIDevice currentDevice] systemVersion] compare:@"7.0"] != NSOrderedAscending )

CGSize size;
NSString *strTail = @"allColorDictallColorDictallColorDtallColorDictallC";
UIFont *font = [UIFont systemFontOfSize:15.0f];
NSDictionary *attribute = @{NSFontAttributeName: font};
if (IOS7_OR_LATER) {
    size = [strTail boundingRectWithSize:self.view.frame.size
                                       options:
                  NSStringDrawingTruncatesLastVisibleLine|
                  NSStringDrawingUsesLineFragmentOrigin|
                  NSStringDrawingUsesFontLeading
                                    attributes:attribute
                                       context:nil].size;
}else{
    size = [strTail sizeWithFont:font constrainedToSize:CGSizeMake(300, 30)];
}

方法二

利用UIView的sizeToFit方法，设置好字体大小，文字内容之后调用即可，size自动就会变化，我们自然也就知道size是多少了，比较方便。

示例代码如下：

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

label.text = @"tallColorDictallColorDictallColorDictallColorDictallColorDtallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorDictallColorD";
[label sizeToFit];
[self.view addSubview:label];

效果如图