使用collectionView 嵌套 collectionView 刷新遇到的坑

[collectionView reloadSections:[NSIndexSet indexSetWithIndex:0]];
[collectionView reloadSections:[NSIndexSet indexSetWithIndex:1]];
[collectionView reloadSections:[NSIndexSet indexSetWithIndex:2]];
[collectionView reloadSections:[NSIndexSet indexSetWithIndex:3]];
[collectionView reloadSections:[NSIndexSet indexSetWithIndex:4]];
[collectionView reloadSections:[NSIndexSet indexSetWithIndex:5]];

当collectionView 分段刷新的时候，部分section contentSize有占用位置 而section却消失不见了

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(nonnull UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(nonnull NSIndexPath *)indexPath
{
    switch (indexPath.section) {
        case 0:{
            //return CGSizeZero;
            return CGSizeMake(375, 0.01f);
            break;
        }
        case 1:{
            //return CGSizeZero;
            return CGSizeMake(375, 0.01f);
            break;
        }
            
        default:
            return CGSizeZero;
            break;
    }
}