Flux on Swift 5.3

FluxSwift5_3.swift

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

    let store = Store<Int, CounterAction>(initialState: 0) { previousState, action in
        switch action  {
        case .increment:
            return previousState + 1
        case .decrement:
            return previousState - 1
        }
    }

    let contentView = ContentView().environmentObject(store)

    // Use a UIHostingController as window root view controller.
    if let windowScene = scene as? UIWindowScene {
        let window = UIWindow(windowScene: windowScene)
        window.rootViewController = UIHostingController(rootView: contentView)
        self.window = window
        window.makeKeyAndVisible()
    }
}

import SwiftUI
import Combine

final class Store<State, Action>: ObservableObject {
    
    typealias Reducer = (State, Action) -> State
    
    private let reducer: Reducer
    
    @Published var state: State
    
    init(initialState: State, reducer: @escaping Reducer) {
        state = initialState
        self.reducer = reducer
    }
    
    func dispatch(action: Action) {
        state = reducer(state, action)
    }
    
}

enum CounterAction {
    case increment
    case decrement
}

struct ContentView: View {

    @EnvironmentObject var store: Store<Int, CounterAction>

    var body: some View {
        VStack {
            VStack(spacing: 30) {
                Text("\(store.state)")
                    .font(.largeTitle)
                HStack {
                    Button {
                        store.dispatch(action: .increment)
                    } label: {
                        Text("Up")
                    }
                    Spacer()
                    Button {
                        store.dispatch(action: .decrement)
                    } label: {
                        Text("Down")
                    }
                }
                .frame(width: 180)
            }
        }
    }
}