How to use reactive programming to subscribe to single-item changes (insertions or deletions) in an array of data?

Question

For context, I am using swift & MVVM architecture to manage a list of data, and a table view that displays it. Reactive patterns (RxSwift or Combine) work well for letting me reload my entire table view when the view model's list data changes.

ViewModel (using RxSwift):

var tableData = BehaviorRelay<[String]>(value: ["First Item", "Second Item"])

ViewController:

var tableView = UITableView()
var disposeBag = DisposeBag()
var viewModel = ViewModel()

init() {
    ...
    viewModel.tableData.subscribe(onNext: { _ in 
       self.tableView.reloadData()
    }).disposed(by: disposeBag)
}

But what if only one item has been inserted or deleted from tableData? In this case, I don't want to call tableView.reloadData(), instead I'd like to use tableView.insertRows(at: <[IndexPath]>, with: <UITableView.RowAnimation>) or tableView.deleteRows(at: <[IndexPath]>, with: <UITableView.RowAnimation>). In order to do this, I need to be able to subscribe to the index paths that have been inserted or removed, instead of the list data as a whole. Does any one know what the most efficient way to do this?

Answer 1

Use UITableViewDiffableDataSource. It takes care of this automatically (reactively) for you.