解决UICollectionView自定义布局出现的警告

最近在项目中遇到一个问题，我自定义布局模仿喵街的时候一直报一个警告，下面是打印：

**UICollectionViewFlowLayout has cached frame mismatch for index path  {length = 2, path = 0 - 0} - cached value: {{0, -170}, {414, 240}}; expected value: {{0, 0}, {414, 0}}**
**2016-05-24 20:02:26.808 SquareTest[4974:409557] This is likely occurring because the flow layout subclass YYSliderViewLayout is modifying attributes returned by UICollectionViewFlowLayout without copying them**

谷歌了很久一直没有找到答案，最后通过如下方式解决了问题，在此记录一下：
原来的方法是：

    NSArray *array = [super layoutAttributesForElementsInRect:correctRect];

将上面的方法改为：

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{

    NSArray *original = [super layoutAttributesForElementsInRect:correctRect];
    NSArray *array =  [[NSArray alloc]initWithArray:original copyItems:YES];  }
 

就搞定了