TCA app make sure you have composable set

App.swift

import SwiftUI
import Combine
import ComposableArchitecture 

struct AppState: Equatable {
    var count = 0
}
enum AppAction: Equatable {
    case decrementButtonTapped
    case incrementButtonTapped
}

enum ExampleError: Error {
    case example
}

struct AppEnvironment {
    var mainQueue: AnySchedulerOf<DispatchQueue>
}

let appReducer = Reducer<AppState, AppAction, AppEnvironment> { state, action, environment in
    switch action {
    case .decrementButtonTapped:
        state.count -= 1
        return .none
    case .incrementButtonTapped:
        state.count += 1
        return .none
    }
}

class CounterViewModel: ObservableObject {
    var viewStore: Store<AppState, AppAction>
    
    init(viewStore: Store<AppState, AppAction>) {
        self.viewStore = viewStore
    }
}

let store = Store(initialState: AppState(), reducer: appReducer, environment: AppEnvironment(mainQueue: .main))
let counterViewModel = CounterViewModel(viewStore: store)

struct CounterView: View {
    @StateObject var viewModel: CounterViewModel
    
    var body: some View {
        WithViewStore(viewModel.viewStore) { store in
            VStack {
                Text("Count \(store.count)")
                    .font(.subheadline.weight(.bold))
                HStack {
                    Button(action: { store.send(.decrementButtonTapped)}, label: { Text("-") })
                    Button(action: { store.send(.incrementButtonTapped) }, label: { Text("+") })
                }
            }
        }
    }
}

struct ContentView: View {
    var body: some View {
        let store = Store(initialState: AppState(), reducer: appReducer, environment: AppEnvironment(mainQueue: .main))
        let counterViewModel = CounterViewModel(viewStore: store)
        
        return VStack {
            CounterView(viewModel: counterViewModel)
        }
    }
}

@main
struct MyApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}