UITableViewDiffableDataSource are not deinit - swift

Question

I want to use a Combine in my project and face the problem.
Here is the code of the ViewController
import Combine
import UIKit
class ProfileDetailsController: ViewController {
//
// MARK: - Views
#IBOutlet private var tableView: UITableView!
// MARK: - Properties
private typealias DataSource = UITableViewDiffableDataSource<ProfileDetailsSection, ProfileDetailsRow>
private typealias Snapshot = NSDiffableDataSourceSnapshot<ProfileDetailsSection, ProfileDetailsRow>
#Published private var data: [ProfileDetailsSectionModel] = {
return ProfileDetailsSection.allCases.map { ProfileDetailsSectionModel(section: $0, data: $0.rows) }
}()
private lazy var dataSource: DataSource = {
let dataSource = DataSource(tableView: tableView) { tableView, _, model in
let cell = tableView.dequeueReusableCell(withIdentifier: TextFieldTableCell.name) as! TextFieldTableCell
cell.delegate = self
cell.setData(model: model)
return cell
}
dataSource.defaultRowAnimation = .fade
return dataSource
}()
}
// MARK: - Setup binding
extension ProfileDetailsController {
override func setupBinding() {
tableView.registerCellXib(cell: TextFieldTableCell.self)
$data.receive(on: RunLoop.main).sink { [weak self] models in
let sections = models.map { $0.section }
var snapshot = Snapshot()
snapshot.appendSections(sections)
models.forEach { snapshot.appendItems($0.data, toSection: $0.section) }
self?.dataSource.apply(snapshot, animatingDifferences: true)
}.store(in: &cancellable)
}
}
// MARK: - Cell delegates
extension ProfileDetailsController: TextFieldTableCellDelegate {
func switcherAction() { }
}
And here is the code of the cell.
import UIKit
protocol TextFieldTableCellData {
var placeholder: String? { get }
}
protocol TextFieldTableCellDelegate: NSObjectProtocol {
func switcherAction()
}
class TextFieldTableCell: TableViewCell {
//
// MARK: - Views
#IBOutlet private var textField: ZWTextField!
// MARK: - Properties
public weak var delegate: TextFieldTableCellDelegate?
override class var height: CGFloat {
return 72
}
}
// MARK: - Public method
extension TextFieldTableCell {
func setData(model: TextFieldTableCellData) {
textField.placeholder = model.placeholder
}
}
ViewController's deinit was not called.
But when I use this code for ViewController
import UIKit
class ProfileDetailsController: ViewController {
//
// MARK: - Views
#IBOutlet private var tableView: UITableView!
// MARK: - Properties
#Published private var data: [ProfileDetailsSectionModel] = {
return ProfileDetailsSection.allCases.map { ProfileDetailsSectionModel(section: $0, data: $0.rows) }
}()
}
// MARK: - Startup
extension ProfileDetailsController {
override func startup() {
tableView.dataSource = self
tableView.registerCellXib(cell: TextFieldTableCell.self)
}
}
// MARK: - Startup
extension ProfileDetailsController: UITableViewDataSource {
func numberOfSections(in tableView: UITableView) -> Int {
return data.count
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return data[section].data.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let model = data[indexPath.section].data[indexPath.row]
let cell = tableView.dequeueReusableCell(withIdentifier: TextFieldTableCell.name) as! TextFieldTableCell
cell.delegate = self
cell.setData(model: model)
return cell
}
}
// MARK: - Cell delegates
extension ProfileDetailsController: TextFieldTableCellDelegate {
func switcherAction() {}
}
Everything is fine. deinit called. I tried to set dataSource optional and set it nil on deinit, the same result. With Combine deinit called only when I comment this line:
cell.delegate = self
Does anyone know what's the matter?
Xcode 13.2 iOS 15.2

Answer 1

The Combine stuff is a total red herring. That's why you can't locate the problem; you're looking in the wrong place. The issue is the difference between an old-fashioned data source and a diffable data source. The problem is here:
private lazy var dataSource: DataSource = { // *
let dataSource = DataSource(tableView: tableView) { tableView, _, model in
let cell = tableView.dequeueReusableCell(withIdentifier: TextFieldTableCell.name) as! TextFieldTableCell
cell.delegate = self // *
I've starred the problematic lines:
On the one hand, you (self, the view controller) are retaining the dataSource.
On the other hand, you are giving the data source a cell provider function in which you speak of self.
That's a retain cycle! You need to break that cycle. Change
let dataSource = DataSource(tableView: tableView) { tableView, _, model in
To
let dataSource = DataSource(tableView: tableView) { [weak self] tableView, _, model in
(That will compile, because although self is now an Optional, so is cell.delegate.)