No reloadData

NoReloadDataTableViewController.swift

// reloadDataを使わないようにしましょう
import UIKit
import DiffableDataSources // https://github.com/ra1028/DiffableDataSources
@available(iOS, introduced: 13.0)
typealias TableViewDiffableDataSource = UITableViewDiffableDataSource

@available(iOS, introduced: 13.0)
typealias DiffableDataSourceSnapshot = NSDiffableDataSourceSnapshot


class NoReloadDataTableViewController: UITableViewController {
    
    struct SectionIdentifier: Identifiable, Hashable {
        let id: Int
    }
    
    struct RowIdentifier: Identifiable, Hashable {
        let id: IndexPath
    }
    
    var reloadCount: Int = 0
    
    lazy private(set) var diffableDataSource: TableViewDiffableDataSource<SectionIdentifier, RowIdentifier> = CustomDataSource(tableView: tableView) { [weak self] (tableView, indexPath, row) -> UITableViewCell? in
        guard let self = self else { return nil }
        
        let cell = self.dequeueCell(forIndexPath: indexPath, row: row)
        self.update(cell: cell, row: row)
        
        return cell
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
        
        navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Remake", style: .plain, target: self, action: #selector(remakeStructure))
        
        diffableDataSource.defaultRowAnimation = .top
        
        remakeStructure()
    }
    
    @objc
    private func remakeStructure() {
        reloadCount += 1
        let sectionCount = (10...50).randomElement()!
        
        var snapshot = DiffableDataSourceSnapshot<SectionIdentifier, RowIdentifier>()
        (0..<sectionCount).forEach { sectionIndex in
            let section = SectionIdentifier(id: sectionIndex)
            snapshot.appendSections([section])
            
            let rowCount = (0...7).randomElement()!
            
            let rows = (0..<rowCount).map { rowIndex in
                RowIdentifier(id: IndexPath(row: rowIndex, section: sectionIndex))
            }
            
            snapshot.appendItems(rows, toSection: section)
        }
        diffableDataSource.apply(snapshot)
        tableView.beginUpdates()
        tableView.indexPathsForVisibleRows?.forEach { indexPath in
            guard let cell = tableView.cellForRow(at: indexPath),
                let row = diffableDataSource.itemIdentifier(for: indexPath)
                else { return }
            update(cell: cell, row: row)
        }
        tableView.endUpdates()
    }
    
    func dequeueCell(forIndexPath indexPath: IndexPath, row: RowIdentifier) -> UITableViewCell {
        tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
    }
    
    func update(cell: UITableViewCell, row: RowIdentifier) {
        cell.textLabel?.text = "Row \(row.id.row), section \(row.id.section). \(reloadCount)"
    }
    
}

class CustomDataSource: TableViewDiffableDataSource<NoReloadDataTableViewController.SectionIdentifier, NoReloadDataTableViewController.RowIdentifier> {
    
    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
         "Section \(section)"
    }
    
}