PaginationTracker

A small library for tracking scrolling in a collection or table view, and triggering page loads as needed.

Overview

Once you've created a tracker, you just need to notify it whenever your view will display a cell, and it'll automatically decide whether it needs to load a new page or not.

Usage

First, create a pagination tracker and store it in a variable in your controller. In your viewDidLoad, ensure you start pagination.

final class NewsController: UITableViewController {
    private lazy var paginationTracker = PaginationTracker(
        nextPageCall: networkClient.loadNextNewsPage
    )

    override func viewDidLoad() {
        super.viewDidLoad()

        // Other setup...

        paginationTracker.startPaging { _ in }
    }
}

Then in your data source implement the willDisplay delegate function so you can update the tracker.

extension NewsController {
    override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        paginationTracker.track(indexPath: indexPath, for: tableView)
    }
}

Pull-to-refresh

If you're adding pull-to-refresh to your view, make sure to trigger a pagination reset.

extension NewsController {
    @IBAction private func refresh() {
        paginationTracker.reset(forceRefresh: true) { [weak self] _ in
            guard let self = self else { return }

            self.refreshControl?.endRefreshing()

            // reload data source, for example an FRC:
            try? self.source.controller.performFetch()
        }
    }
}

The forceRefresh parameter is set to true here, so that you can check whether you need to delete old data during your import:

extension News {
    func didImport(...) {
        let pagination: PaginationContext<News> = ...

        if pagination.forceRefresh {
            // Delete all old news items
        }
    }
}

Pagination Context

The next page call is defined as follows:

typealias NextPageCall = (_ context: PaginationContextWithObject<Page, ContextObject>, _ handler: @escaping (Result<Page>) -> Void) -> Void

If during your pagination, you need to have a certain context object/information, you can use the following initializer instead:

final class NewsController: UITableViewController {
    private var category: NewsCategory

    private lazy var paginationTracker = PaginationTrackerWithContext(
        nextPageCall: networkClient.loadNextPage,
        contextObject: category
    )
}

Now you can access this object in the next page call:

func loadNextPage(_ context: PaginationContextWithObject<NewsPage, NewsCategory>, _ handler: @escaping (Result<NewsPage>) -> Void) {
    // get pagination context object (a news category)
    let newsCategory = context.object
}

StatefulUI integration

PaginationTracker easily integrates with the StatefulUI library, you just need to provide the StatefulViewController during initialization:

final class NewsController: UITableViewController {
    private lazy var paginationTracker = PaginationTracker(
        nextPageCall: networkClient.loadNextNewsPage,
        statefulController: self
    )
}

extension NewsController: StatefulViewController {
    // Stateful implementation...
}

The tracker will automatically set the correct state, whether it is loading a page, has no content or an error occurred.

Installation

CocoaPods

Add the following line to your Podfile.

pod "PaginationTracker", "~> 1.0"

Then run pod install with CocoaPods 1.4 or newer.

Contributing

Create something awesome, make the code better, add some functionality, whatever (this is the hardest part).
Fork it
Create new branch to make your changes
Commit all your changes to your branch
Submit a pull request

Credits

PaginationTracker is brought to you by David Jennes.

License

PaginationTracker is available under the MIT license. See the LICENSE file for more info.

wassup- / PaginationTracker