'NSInternalInconsistencyException', reason: 'UICollectionView received layout attributes for a ...

swift3.0自定义UICollectionViewLayout 当数据改变collectionView.reloadData()时出现如下错误:

'NSInternalInconsistencyException', reason: 'UICollectionView received layout attributes for a cell with an index path that does not exist: {length = 2, path = 10 - 0}'

经过不断调试，出现这种情况的原因是数据切换时数组长度变化，但是UICollectionViewLayout中定义的itemAttributes并没有清空。还是拿的reloadData()之前的数据

解决办法:在继承了UICollectionViewLayout的类中重写以下方法，将itemAttributes置为空

 overridefunc invalidateLayout() {

        super.invalidateLayout()

        itemAttributes =nil

    }