ViewController.swift

//
//  ViewController.swift
//  DiffableTest
//
//  Created by Paul Wilkinson on 28/9/20.
//

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var tableview: UITableView!
    let identifier = "Cell"
    
    var dataSource: UITableViewDiffableDataSource<Section, RowData>! = nil
    var currentSnapshot: NSDiffableDataSourceSnapshot<Section, RowData>! = nil
    var arrItems = [RowData]()
    var dateFormatter: DateFormatter = {
        let df = DateFormatter()
        df.timeStyle = .medium
        df.dateStyle = .short
        return df
    }()
    
    var timer: Timer?
    
    override func viewDidLoad() {
        super.viewDidLoad()
  
        for i in 0...20 {
            arrItems.append(RowData(name: "Row \(i)"))
        }
        configureDataSource()
        updateUI()
        self.timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { (timer) in
            guard let datasource = self.tableview.dataSource as? UITableViewDiffableDataSource<Section,RowData> else {
                return
            }
            var snapshot = datasource.snapshot()
            var rowIdentifers = Set<RowData>()
            for _ in 0...Int.random(in: 1...self.arrItems.count) {
                let randomIndex = Int.random(in: 0...self.arrItems.count-1)
             
                self.arrItems[randomIndex].timeStamp = Date()
            
                rowIdentifers.insert(self.arrItems[randomIndex])
            }
            snapshot.reloadItems(Array(rowIdentifers))
            datasource.apply(snapshot)
        }
    }
    
    func updateUI(animated: Bool = true) {
            currentSnapshot = NSDiffableDataSourceSnapshot<Section, RowData>()
            currentSnapshot.appendSections([.main])
            currentSnapshot.appendItems(arrItems, toSection: .main)
            self.dataSource.apply(currentSnapshot, animatingDifferences: animated)
        }

    func configureDataSource() {
            
            self.dataSource = UITableViewDiffableDataSource
                <Section, RowData>(tableView: tableview) {
                    (tableView: UITableView, indexPath: IndexPath, item: RowData) -> UITableViewCell? in
                    
                let newItem = self.arrItems[indexPath.row]
                    let cell = tableView.dequeueReusableCell(
                        withIdentifier: self.identifier,
                        for: indexPath)
                cell.textLabel?.text = newItem.name
                cell.detailTextLabel?.text = self.dateFormatter.string(from: newItem.timeStamp)
                cell.backgroundColor = newItem.color
                    
                    return cell
            }
            self.dataSource.defaultRowAnimation = .fade
            
        }

}

enum Section: CaseIterable {
    case main
}


struct RowData: Hashable {
    var id: UUID = UUID()
    var name: String
    private let possibleColors: [UIColor] = [.yellow,.orange,.cyan]
    dynamic var timeStamp = Date()
    
    var color: UIColor {
        return possibleColors.randomElement()!
    }
    
    func hash(into hasher: inout Hasher) {
        hasher.combine(self.id)
    }
    
    static func ==(lhs: RowData, rhs: RowData) -> Bool {
        return lhs.id == rhs.id
    }
}