NestedClosureWeakSelf.swift

class Cell {
  private let viewBlock: () -> Void

  init(viewBlock: @escaping () -> Void) {
    self.viewBlock = viewBlock
  }

  deinit {
    print(type(of: self), #function)
  }

  func loadView() {
    self.viewBlock()
  }
}

class DataSource {
  private let configureCell: () -> Cell

  init(configureCell: @escaping () -> Cell) {
    self.configureCell = configureCell
  }

  deinit {
    print(type(of: self), #function)
  }

  func cell() -> Cell {
    let cell = self.configureCell()
    cell.loadView()
    return cell
  }
}

class ViewController {
  private let name: String = "A"
  private lazy var dataSource: DataSource = DataSource(configureCell: { [weak self] in // 1: Required
    // guard let self = self else { return ... }
    return Cell(viewBlock: { [weak self] in // 2: Required only after strongify self
      print(self?.name)
    })
  })
  private var cells: [Cell] = []

  init() {
    self.cells.append(self.dataSource.cell())
  }

  deinit {
    print(type(of: self), #function)
  }
}

_ = {
  _ = ViewController()
}()