iOS 在collectionView顶部无缝插入数据效果

想要达到类似抖音在顶部插入数据的效果，不能用peformbatchupdate, 因为他的回调会有延迟，这里要先调用
[CATransaction setDisableActions:YES]; 关闭动画效果，然后在顶部插入数据，之后在滚动到插入之前的第一个数据的位置，就达到了从视觉上插入的效果
直接上代码

- (void)insertFeedsAtTop:(NSArray<NSObject *> *)instances completion:(void (^)(BOOL))completion
{
    if (instances.count == 0) {
        completion ? completion(YES) : nil;
    }
    dispatch_sync_on_main_queue(^{
        NSMutableArray *privateCardInstances = [self valueForKey:@"dataSource"]];
        if (![privateCardInstances isKindOfClass:[NSMutableArray class]]) {
            return;
        }
        
        [CATransaction setDisableActions:YES];
        NSIndexSet *idxs = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, instances.count)];
        [privateCardInstances insertObjects:instances atIndexes:idxs];
        NSInteger endItem = 0;
        for (CSCardInstance *pIns in instances) {
            endItem += pIns.children.count;
        }
        NSMutableArray *indexPathes = NSMutableArray.new;
        for (NSInteger j = 0; j < endItem; j++) {
            [indexPathes addObject:[NSIndexPath indexPathForItem:j inSection:0]];
        }
        [self.collectionView insertItemsAtIndexPaths:indexPathes];
        [CATransaction setDisableActions:NO];
        if (completion) {
            completion(YES);
        }
    });
}