自定义UICollectionViewFlowLayout打印错

自定义UICollectionViewFlowLayout后打印如下错误：

Warning: UICollectionViewFlowLayout has cached frame mismatch for index path 'xxx'

解决方法：

NSArray * original   = [super layoutAttributesForElementsInRect:rect];
NSArray * attributes = [[NSArray alloc] initWithArray:original copyItems:YES];

链接：https://stackoverflow.com/questions/31508153/warning-uicollectionviewflowlayout-has-cached-frame-mismatch-for-index-path-ab