iOS 10的UICollectionViewDataSourcePrefetching方法

iOS 10的Tableview 和 CollectionView 出了一个新的DataSourcePrefetching代理。用于解决滑动时候的时候，让页面滑动的时候更加流畅。

应该是这样用的：

- (void)collectionView:(UICollectionView *)collectionView prefetchItemsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths{
    
    for (NSIndexPath *indexPath in indexPaths) {
        if (indexPath.section == self.section && indexPath.item<self.deviceDataSource.count) {
            WZBLEDataModel *model = self.deviceDataSource[indexPath.item];
            WSTHomeDeviceCell *cell = (WSTHomeDeviceCell *)[collectionView cellForItemAtIndexPath:indexPath];
            [cell refreshWithModel:model indexPath:indexPath];
        }
        
    }
}

- (void)collectionView:(UICollectionView *)collectionView cancelPrefetchingForItemsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths{
    for (NSIndexPath *indexPath in indexPaths) {
        if (indexPath.section == self.section && indexPath.item<self.deviceDataSource.count) {
            if (self.deviceDataSource[indexPath.item]) {
                WZBLEDataModel *model = self.deviceDataSource[indexPath.item];
                model = nil;
            }
        }
    }
    
}