RxSwift tableView update based on property - reactive-programming

Question

I have a UITableView populated with Product models. There are 2 challenges I'm having right now. The first is I have a quantityLabel on the cells which I want to update when the user presses an increment or decrement button on the cell. Currently to do this, I am updating the model and accepting an entirely new array, which triggers the tableView to reload, which isn't ideal. The second challenge is, when the quantity of a Product goes to 0, that cell should be removed from the tableView with an animation. Currently, I just find the index of the product within the dataSource, remove it and reload the table. I'd like to know the proper Rx way to do this. Here's a sample of my code. Thanks!
struct Product: Equatable {
var i: String
var quantity: Int
init(i: Int, quantity: Int) {
self.i = "item: \(i)"
self.quantity = quantity
}
}
extension Product {
static func ==(lhs: Product, rhs: Product) -> Bool {
return lhs.i == rhs.i
}
}
class ProductSource {
var items: BehaviorRelay<[Product]> = BehaviorRelay<[Product]>(value: [])
var itemsObservable: Observable<[Product]>
init() {
itemsObservable = items.asObservable().share(replay: 1)
items.accept((0..<20).map { Product(i: $0, quantity: 2) })
}
func add(product: Product) {}
func remove(product: Product) {
guard let index = self.items.value.index(of: product) else {return}
// decrement quantity, if quantity is 0, remove from the datasource and update the tableView
}
}
class ViewController: UIViewController {
#IBOutlet weak var tableView: UITableView!
var disposeBag = DisposeBag()
var data = ProductSource()
override func viewDidLoad() {
super.viewDidLoad()
tableView.rx.setDelegate(self).disposed(by: disposeBag)
data.itemsObservable
.bind(to: tableView.rx.items(cellIdentifier: "productCell", cellType: ProductTableViewCell.self)) { row, element, cell in
cell.nameLabel.text = element.i
cell.quantityLabel.text = String(element.quantity)
}.disposed(by: disposeBag)
}
}
extension ViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 100
}
}

Answer 1

Both of your challenges can be solved by using the RxDataSources Cocoapod.
Alternatively, you could roll your own like I did here: https://github.com/dtartaglia/RxMultiCounter/blob/master/RxMultiCounter/RxExtensions/RxSimpleAnimatableDataSource.swift
The idea here is to use something (I'm using DifferenceKit) to figure out which elements changed and only reload those particular elements. To do this, you need a specialized data source object, not the generic one that comes with RxCocoa.