IGListKit/Examples/Examples-iOS/IGListKitExamples/ViewControllers/AnnouncingDepsViewController.swift

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import IGListKit
import UIKit

final class AnnouncingDepsViewController: UIViewController, ListAdapterDataSource {

    lazy var adapter: ListAdapter = {
        return ListAdapter(updater: ListAdapterUpdater(), viewController: self, workingRangeSize: 1)
    }()
    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
    let data: [NSNumber] = Array(0..<20).map { NSNumber(value: $0) }
    let announcer = IncrementAnnouncer()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(collectionView)
        adapter.collectionView = collectionView
        adapter.dataSource = self

        // disable prefetching so cells are configured as they come on screen
        if #available(iOS 10.0, *) {
            collectionView.isPrefetchingEnabled = false
        }

        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .add,
                                                            target: self,
                                                            action: #selector(AnnouncingDepsViewController.onAdd))
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        collectionView.frame = view.bounds
    }

    @objc func onAdd() {
        announcer.increment()
    }

    // MARK: ListAdapterDataSource

    func objects(for listAdapter: ListAdapter) -> [ListDiffable] {
        return data
    }

    func listAdapter(_ listAdapter: ListAdapter, sectionControllerFor object: Any) -> ListSectionController {
        return ListeningSectionController(announcer: announcer)
    }

    func emptyView(for listAdapter: ListAdapter) -> UIView? {
        return nil
    }

}