11_simple-combine-framework-testbed.swift

import SwiftUI
import Combine

// original code for CancellerWrapper was posted on @Cockscomb cockscomb's blog post. https://cockscomb.hatenablog.com/entry/2021/09/26/103128
class CancellerWrapper<Wrapped> {
    var value: Wrapped
    init(_ value: Wrapped) { self.value = value }
}

class SimpleModel: UIResponder, ObservableObject {
    struct State {
        var items: [Int]
    }
    @Published var state = State(items: [])
}

struct ContentView: View {
    @StateObject var simpleModel: SimpleModel
    let cancellables: CancellerWrapper<Set<AnyCancellable>> = .init(Set<AnyCancellable>())
    var body: some View {
        NavigationView {
            Text("Simple Combine Framework SimpleCombineFrameworkTestbed")
                .padding()
                .onAppear {
                    simpleModel.$state.map(\.items).sink(receiveValue: { items in
                        print("items.count=\(items.count)")
                    }).store(in: &self.cancellables.value)

                }
                .navigationTitle(Text("Testbed"))
                .navigationBarItems(trailing:
                    Button(action: {
                        simpleModel.state.items = [1,2,3,4,5]
                    }, label: { Text("Execute") })
                )
        }
    }
}

@main
struct SimpleCombineFrameworkTestbedApp: App {
    var simpleModel = SimpleModel()
    var body: some Scene {
        WindowGroup {
            ContentView(simpleModel: simpleModel)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var simpleModel = SimpleModel()
    static var previews: some View {
        ContentView(simpleModel: Self.simpleModel)
    }
}