UIKit ListsOfState Case Study: Why the local dataSource var in the ViewController?

[ryanbooker]

I've just been looking through the UIKit case studies, and I noticed that the ListsOfState example have a dataSource var.

Why is that? Is there a particular reason?

At first glance, it just looks like a way to call tableView.reloadData, and it's trivial to remove, and call reloadDatainstead, while using the viewStore directly in the tableView delegate calls.

[mbrandonw]

Hey @ryanbooker, the dataSource variable is what powers the UITableViewDataSource conformance. For example, it determines the number of rows in the table view:

swift-composable-architecture/Examples/CaseStudies/UIKitCaseStudies/ListsOfState.swift

Lines 56 to 58 in 11f215c

	override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
	self.dataSource.count
	}

And the label for the cell at a particular row:

swift-composable-architecture/Examples/CaseStudies/UIKitCaseStudies/ListsOfState.swift

Line 65 in 11f215c

cell.textLabel?.text = "\(self.dataSource[indexPath.row].count)"

To me it seems necessary to implement the data source protocol. Could you explain a bit more about how it's trivial to remove? I may be missing something.

[ryanbooker]

I think my question boils down to, why not:

self.viewStore.publisher.counters
  .sink(receiveValue: { [weak self] _ in self?.tableView.reloadData() })
  .store(in: &cancellables)

and in the UITableViewDataSource

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 
  viewStore.counters.count 
} 

and

cell.textLabel?.text = "\(viewStore.counters[indexPath.row].count)"

I could be missing something too… I'm still getting my head around all this. :)

[mbrandonw]

Oh, haha. Yes, I suppose it could be! I'm not sure why we did it like that. I guess we just felt it was more recognizable to iOS devs to see an explicit data source ¯\(ツ)/¯

[stephencelis]

I don't think you're missing anything 😅. I think it was just a pre-TCA habit of having a "data source" around. Looks like we can simplify things: #365

[abdelmajidrajad]

I also want to ask @brandon Williams <mbw234@gmail.com> about the best approach to take to have a viewStore for each cell on UIKit. having a setter like: cell.viewStore = viewStore is an ultimate solution ? Thanks for taking time for this.

…

On Tue, 26 Jan 2021 at 11:12, Ryan Booker ***@***.***> wrote: I think my question boils down to, why not: self.viewStore.publisher.counters .sink(receiveValue: { [weak self] _ in self?.tableView.reloadData() }) .store(in: &self.cancellables) and in the UITableViewDataSource override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { self.viewStore.counters.count } and cell.textLabel?.text = "\(self.viewStore.counters[indexPath.row].count)" I could be missing something too… I'm still getting my head around all this. :) — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#351 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADDCYOHXBXDUFXLTXAD6APLS32ISRANCNFSM4WFEEBUA> .

[mbrandonw]

Yeah that seems fine to me. It might also be possible to cook up a Store.forEach operator that mimics the ForEachStore view in SwiftUI (we already have Store.ifLet that mimics IfLetStore), which would allow you to pass a Store to each cell and then turn it into a ViewStore inside the cell. But we haven't given much thought to that yet.

[mluisbrown]

Hi @mbrandonw, two of my co-workers (@gtsiap and @ekoutkias) created a version of Store.forEach for use in our project at XM where we are using the ReactiveSwift TCA with UIKit. It uses ReactiveSwift but should be easy to convert to Combine

import ComposableArchitecture
import Foundation
import ReactiveSwift

extension Store where State: Equatable {
    public func forEach<LocalState: Equatable, LocalAction>(
        state: @escaping (State) -> [LocalState],
        action: @escaping ((Int, LocalAction)) -> Action
    ) -> [Store<LocalState, LocalAction>] {
        let scopedStore = scope(state: state)
        let viewStore = ViewStore(scopedStore)
        let localStores = zip(viewStore.indices, viewStore.state).map { index, element in
            scopedStore.scope(
                state: { index < $0.endIndex ? $0[index] : element },
                action: { action((index, $0)) }
            )
        }
        return localStores
    }

    public func forEach<LocalState: Equatable, LocalAction>(
        state: @escaping (State) -> [LocalState],
        action: @escaping (LocalAction) -> Action
    ) -> [Store<LocalState, LocalAction>] {
        let scopedStore = scope(state: state)
        let viewStore = ViewStore(scopedStore)
        let localStores = zip(viewStore.indices, viewStore.state).map { index, element in
            scopedStore.scope(
                state: { index < $0.endIndex ? $0[index] : element },
                action: { action($0) }
            )
        }
        return localStores
    }
}

[abdelmajidrajad]

Thanks Brandon.

…

On Tue, 26 Jan 2021 at 15:49, Brandon Williams ***@***.***> wrote: Yeah that seems fine to me. It might also be possible to cook up a Store.forEach operator that mimics the ForEachStore view in SwiftUI (we already have Store.ifLet that mimics IfLetStore), which would allow you to pass a Store to each cell and then turn it into a ViewStore inside the cell. But we haven't given much thought to that yet. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#351 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADDCYOCBZKZUJEL7R6IZVOTS33JA5ANCNFSM4WFEEBUA> .