Load More data on Scroll Demand on CollectionView - ios

Question

I am implementing a feature on the collectionView where user scrolls the collectionView at the bottom (20 items) and it requests another set of data (20 more items) from the server.
I have implemented the following two approaches. But I wonder which approach is better? or is there any other better approach which I am not aware of?
The first approach is to use the indexPath in the cellForItemAtIndexPath as follows
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
if(collectionView == productCollectionView)
{
__weak ProductCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
// load more data
if(indexPath.row == numberOfItemsPerSection-1)
{
numberOfItemsPerSection += 20;
offset += 20;
[self loadFromURL];
}
// loading image and text happening here.
// it is not included here
return cell;
}
}
The second approach is to scrollViewDidScroll as follows
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
if (scrollView.contentOffset.y == scrollView.contentSize.height - scrollView.frame.size.height && pElements.count == numberOfItemsPerSection) {
numberOfItemsPerSection += 20;
offset += 20;
[self loadFromURL];
}
}

Answer 1

I do this thing through CollectionViewDelegate method like:
- (void)collectionView:(UICollectionView *)collectionView
willDisplayCell:(UICollectionViewCell *)cell
forItemAtIndexPath:(NSIndexPath *)indexPath{
if indexPath.row == numberOfitem.count-1 && !self.waiting {
waiting = true;
self.loadMoreData()
}
}
-(void)loadMoreData(){
// After getting the response then
[numberOfitem addObjects : your response in term of array];
waiting = false;
}
In swift 4.0
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
// Note: ‘isWating’ is used for checking the paging status Is currency process or not.
if indexPath.section == self.dataSoruce.list.count - 2 && !isWating {
isWating = true
self.pageNumber += 1
self.doPaging()
}
}
private func doPaging() {
// call the API in this block and after getting the response
self.dataSoruce.append(newData);
self.tableView.reloadData()
self.isWating = false // it means paging is done and the user can able request another page request via scrolling the table view at the bottom.
}

Answer 2

Swift 3 : CollectionView Delegate method
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
if indexPath.row == numberofitem.count - 1 { //numberofitem count
updateNextSet()
}
}
func updateNextSet(){
print("On Completetion")
//requests another set of data (20 more items) from the server.
}

Answer 3

Swift 4.2
When you call reloadData() inside CollectionView delegate method you will see blank cells. You need call it like this.
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
if indexPath.row == collectionView.numberOfItems(inSection: indexPath.section) - 1 {
updateNextSet()
}
}
func updateNextSet(){
print("On Completetion")
//requests another set of data (20 more items) from the server.
DispatchQueue.main.async(execute: collectionView.reloadData)
}