UICollectionView triggers pagination without scrolling - ios

Question

I want to achieve a smooth pagination experience in UICollectionView. The idea is simple: trigger an API call when the last cell of collectionView is reached.
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if indexPath.row == dataGroup.data.count-1{
print("last cell visible" )
self.isPaginating = true
Service.shared.fetchData(page: self.page) { rawData, error in
if let error = error{
print("error while fetching app groups", error)
return
}
sleep(2)
if let data = rawData{
self.dataGroup?.data += data.data
DispatchQueue.main.async {
self.collectionView.reloadData()
}
self.page+=1
self.isPaginating = false
}
}
}
//returning cells
}
Even though I don't scroll the collectionView, if indexPath.row == dataGroup.data.count-1 becomes true and the API call is triggered. What can be the cause?
PS. I observe the data.count and pagination stops when all the data is loaded. I just removed it to simplify the code in the question.

Answer 1

Try to move your code in
collectionView(_ collectionView: UICollectionView,
willDisplay cell: UICollectionViewCell,
forItemAt indexPath: IndexPath)
https://developer.apple.com/documentation/uikit/uicollectionviewdelegate/1618087-collectionview
And add check like :
if collectionView.indexPathsForVisibleItems.lastObject.row == dataGroup.data.count-1. {
do something
}