Btukfyl

I'm trying to implement an infinite scroll/pagination feature to a table view. I use scrollViewDidScroll to measure when the user reaches the bottom of the page, which then triggers a function to fetch the next batch of data. However I think the measurements are off because my fetchMoreEvents function is being triggered upon the launch of the app.

This is the pagination code (scrollViewDidScroll and fetchMoreEvents):

func fetchMoreEvents() {

    fetchingMore = true

    var page = 1

    page += 1



    let seatGeekApiUrl = URL(string: "https://api.seatgeek.com/2/events?venue.state=NY&page=(page)&client_id=MTM5OTE0OTd8MTU0MjU2NTQ4MC4z")!



    fetchData(url: seatGeekApiUrl) { (result: FetchResult<Welcome>) -> (Void) in



        switch result {

        case .success(let object): self.eventData.append(contentsOf: object.events)

            print("neventData: nn(self.eventData)")

        case .failure(let error):

            print("nError decoding JSON: nn(error)")

        }

        DispatchQueue.main.async {

            self.tableView.reloadData()

        }

    }



    print("nFetching next batch of events: (Page (page))n")

}



override func scrollViewDidScroll(_ scrollView: UIScrollView) {

    let offsetY = scrollView.contentOffset.y

    let contentHeight = scrollView.contentSize.height



    if offsetY > contentHeight - scrollView.frame.height {

        if !fetchingMore {

            fetchMoreEvents()

        }

    }

}

Once fetchMoreEvents is triggered, I have it append my eventData array with the next page of results and reload the table view. My print statement confirms that it fetches page 2 of the data, but like I said that happens immediately instead of when I scroll down the page. Also, it never gets triggered again.

Is this an issue with the measurements in scrollViewDidScroll, or am I going wrong somewhere else?

These are the table view methods if they're applicable here:

override func numberOfSections(in tableView: UITableView) -> Int {

    return 2

}



override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    if section == 0 {

        return eventData.count

    } else if section == 1 && fetchingMore {

        return 1

    }

    return 0

}



override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    if indexPath.section == 0 {

        let cell = tableView.dequeueReusableCell(withIdentifier: "eventsCell", for: indexPath) as! EventsTableViewCell



        let event = eventData[indexPath.row]



        // Labels

        cell.eventNameLabel.text = event.title

        cell.eventVenueLabel.text = event.venue.nameV2

        cell.eventAddressLabel.text = event.venue.address

        cell.eventTimeLabel.text = dateFormatter.string(from: event.dateTimeLocal)



        // Image

        if let urlString = event.performers[0].image, let imageURL = URL(string: urlString) {

            ImageService.getImage(url: imageURL) { (image) in

                cell.eventImageView.image = image

            }

        }

        else {

            cell.eventImageView.image = UIImage(named: "noImageFound")

        }



        return cell

    } else {

        let cell = tableView.dequeueReusableCell(withIdentifier: "loadingCell", for: indexPath) as! LoadingCell



        cell.spinner.startAnimating()



        return cell

    }

}

Declare an Bool as property

var isAllRowSeeked: Bool = false

Put this logic in your scrollViewDidScroll

let  height = scrollView.frame.size.height

let contentYoffset = scrollView.contentOffset.y

let distanceFromBottom = scrollView.contentSize.height - contentYoffset

if distanceFromBottom < height,

   self.isAllRowSeeked == true {

   // you've reached the end, you are now ready to load more data



   self.isAllRowSeeked = false

}

Now in cellForRowAtIndexPath

 if  fetchingMore == true,

        isLastSectionRow(indexPath: indexPath) {// it's the last row of this section

        state.isAllRowSeeked = true

        return paginatorUI?.getPaginatedLoadMoreCell()

    } else {

        return nil

    }

Add the following method

public func isLastSectionRow(indexPath: IndexPath) -> Bool {

            let lastSection = tableview.dataSource?.numberOfSections?(in: tableview)

                ?? 1

            let lastRow = tableview.dataSource?.tableView(tableview,

                                                          numberOfRowsInSection: indexPath.section)

                ?? 0



            return lastSection == (indexPath.section+1) && lastRow == (indexPath.row+1)

    }

Actually this logic is borrowed from one of my pod, which you can use. Complete code for this pagination can be found here