IGListKit/Examples/Examples-iOS/IGListKitExamples/ViewControllers/DiffTableViewController.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 Person: ListDiffable {

    let pk: Int
    let name: String

    init(pk: Int, name: String) {
        self.pk = pk
        self.name = name
    }

    func diffIdentifier() -> NSObjectProtocol {
        return pk as NSNumber
    }

    func isEqual(toDiffableObject object: ListDiffable?) -> Bool {
        guard let object = object as? Person else { return false }
        return self.name == object.name
    }

}

final class DiffTableViewController: UITableViewController {

    let oldPeople = [
        Person(pk: 1, name: "Kevin"),
        Person(pk: 2, name: "Mike"),
        Person(pk: 3, name: "Ann"),
        Person(pk: 4, name: "Jane"),
        Person(pk: 5, name: "Philip"),
        Person(pk: 6, name: "Mona"),
        Person(pk: 7, name: "Tami"),
        Person(pk: 8, name: "Jesse"),
        Person(pk: 9, name: "Jaed")
    ]
    let newPeople = [
        Person(pk: 2, name: "Mike"),
        Person(pk: 10, name: "Marne"),
        Person(pk: 5, name: "Philip"),
        Person(pk: 1, name: "Kevin"),
        Person(pk: 3, name: "Ryan"),
        Person(pk: 8, name: "Jesse"),
        Person(pk: 7, name: "Tami"),
        Person(pk: 4, name: "Jane"),
        Person(pk: 9, name: "Chen")
    ]
    lazy var people: [Person] = {
        return self.oldPeople
    }()
    var usingOldPeople = true

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .play,
                                                            target: self,
                                                            action: #selector(DiffTableViewController.onDiff))
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
    }

    @objc func onDiff() {
        let from = people
        let to = usingOldPeople ? newPeople : oldPeople
        usingOldPeople = !usingOldPeople
        people = to

        let result = ListDiffPaths(fromSection: 0, toSection: 0, oldArray: from, newArray: to, option: .equality).forBatchUpdates()

        tableView.beginUpdates()
        tableView.deleteRows(at: result.deletes, with: .fade)
        tableView.insertRows(at: result.inserts, with: .fade)
        result.moves.forEach { tableView.moveRow(at: $0.from, to: $0.to) }
        tableView.endUpdates()
    }

    // MARK: UITableViewDataSource

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return people.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        cell.textLabel?.text = people[indexPath.row].name
        return cell
    }

}