UIKit table view cell reuse

TableCellReuse.swift

import UIKit
import PlaygroundSupport

class Cell: UITableViewCell {
  override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
    super.init(style: style, reuseIdentifier: reuseIdentifier)
  }
  
  required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  
  override func prepareForReuse() {
    super.prepareForReuse()
  }
}

class IndexPathCell {
  var indexPath: IndexPath
  let cell: UITableViewCell
  
  init(indexPath: IndexPath, cell: UITableViewCell) {
    self.indexPath = indexPath
    self.cell = cell
  }
}

class MyTableView: UITableView {
  var identifierIndexPathCells = [String: [IndexPathCell]]()
  var identifierClass = [String: AnyClass]()
  
  func dequeueMyReusableCell(withIdentifier identifier: String, for indexPath: IndexPath) -> UITableViewCell {
        
    var indexPathCells = identifierIndexPathCells[identifier] ?? []
    defer { identifierIndexPathCells[identifier] = indexPathCells }
        
    let visibleIndexPaths = indexPathsForVisibleRows ?? []
    let scrollingDown = indexPath.row > (indexPathCells.last?.indexPath.row ?? -1)
    
    if scrollingDown {
      if let indexPathCell = indexPathCells.first, (!visibleIndexPaths.contains(indexPathCell.indexPath) || indexPathCell.cell.isHidden)  {
        indexPathCells.removeFirst()
        indexPathCells.append(indexPathCell)
        indexPathCell.indexPath = indexPath
        indexPathCell.cell.prepareForReuse()
        return indexPathCell.cell
      }
    } else {
      if let indexPathCell = indexPathCells.last, (!visibleIndexPaths.contains(indexPathCell.indexPath) || indexPathCell.cell.isHidden) {
        indexPathCells.removeLast()
        indexPathCells.insert(indexPathCell, at: 0)
        indexPathCell.indexPath = indexPath
        indexPathCell.cell.prepareForReuse()
        return indexPathCell.cell
      }
    }
        
    guard let aClass = identifierClass[identifier] else {
      preconditionFailure("cell not registered")
    }
    
    guard let CellClass = aClass as? UITableViewCell.Type else {
      preconditionFailure("classs not of UITableViewCell type")
    }
    
    let cell = CellClass.init(style: .default, reuseIdentifier: identifier)
    let indexPathCell = IndexPathCell(indexPath: indexPath, cell: cell)
    if scrollingDown {
      indexPathCells.append(indexPathCell)
    } else {
      indexPathCells.insert(indexPathCell, at: 0)
    }
    return cell
  }
  
  func registerMy(_ cellClass: AnyClass?, forCellReuseIdentifier identifier: String) {
    identifierClass[identifier] = cellClass
  }
}

class DataSource: NSObject, UITableViewDataSource {
  private static let identifier = "cell"
  
  init(tableView: UITableView) {
    super.init()
    (tableView as! MyTableView).registerMy(Cell.self, forCellReuseIdentifier: DataSource.identifier)
  }
  
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return 100
  }
  
  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = (tableView as! MyTableView).dequeueMyReusableCell(withIdentifier: DataSource.identifier, for: indexPath)
    cell.textLabel?.text = "\(indexPath.row + 1)"
    return cell
  }
}

let tableView = MyTableView(frame: CGRect(origin: .zero, size: CGSize(width: 200, height: 400)))
let dataSource = DataSource(tableView: tableView)
tableView.dataSource = dataSource

PlaygroundPage.current.setLiveView(tableView)