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);}});
}