RxSwift. What to use for Observable<Void>? - swift

Question

Writing a project on MVVM and trying to bind everything with RxSwift.
Unfortunately I did not manage to find a proper way how to bind an actions.
For example, I have a table and a simple cells with one button - "Select".
For this purposes I will have two view models: ListViewModel & CellViewModel
ListViewModel will be creating an array of CellViewModel and need to subscribe on selection event(custom event).
Now I'm using BehaviorSubject for this purposes, but it looks ugly. Who can point me how it need to be implemented with RxSwift?
class CellViewModel {
private let selectionSubject = BehaviorSubject<Void>(value: ())
// Will be used by ListViewModel
var selectionObservable: Observable<Void> {
return selectionSubject.asObservable()
}
func subscribeOnSelection(_ observable: Observable<Void>, disposeBag: DisposeBag) {
observable
.bind(to: selectionSubject)
.disposed(by: disposeBag)
}
private func autoSelect() {
selectionSubject.on(next: ())
}
}
class Cell: UITableViewCell {
#IBOutlet private var selectionButton: UIButton!
private let disposeBag = DisposeBag()
func bind(to viewModel: CellViewModel) {
viewModel.subscribeOnSelection(selectionButton.rx.tap.asObservable(), disposeBag: disposeBag)
}
}

Answer 1

You need a subject somewhere because the emitter of the event doesn't exist when the consumer of the event is created. Normally I put a single subject in the view controller rather than a subject in every cell. Something like this:
class Cell: UITableViewCell {
#IBOutlet private var selectionButton: UIButton!
private var disposeBag = DisposeBag()
override func prepareForReuse() {
super.prepareForReuse()
disposeBag = DisposeBag()
}
func configure(with makeViewModel: (Observable<Void>, DisposeBag) -> Void) {
makeViewModel(selectionButton.rx.tap.asObservable(), disposeBag)
}
}
And the view controller would look something like:
class ViewController: UIViewController {
#IBOutlet weak var tableView: UITableView!
let disposeBag = DisposeBag()
var makeViewModel: (Observable<CellID>) -> Observable<[CellID]> = { _ in fatalError() }
override func viewDidLoad() {
super.viewDidLoad()
let cellSelection = PublishSubject<CellID>()
let cells = makeViewModel(cellSelection)
cells
.bind(to: tableView.rx.items(cellIdentifier: "Cell", cellType: Cell.self)) { index, element, cell in
cell.configure(with: { selected, disposeBag in
selected
.map { element }
.bind(to: cellSelection)
.disposed(by: disposeBag)
})
return
}
.disposed(by: disposeBag)
}
}