MVVM vs TCA Comparison

// MVVM - Product list
import SwiftUI
import Observation

@Observable
class ProductListViewModel {
    var products: [Product] = []
    var isLoading = false
    var errorMessage: String?
    var searchText = ""

    private let repository: ProductRepository

    init(repository: ProductRepository = .live) {
        self.repository = repository
    }

    var filteredProducts: [Product] {
        guard !searchText.isEmpty else { return products }
        return products.filter { $0.name.localizedCaseInsensitiveContains(searchText) }
    }

    func loadProducts() async {
        isLoading = true
        errorMessage = nil
        do {
            products = try await repository.fetchProducts()
        } catch {
            errorMessage = "Failed to load products: \\(error.localizedDescription)"
        }
        isLoading = false
    }

    func deleteProduct(_ product: Product) async {
        do {
            try await repository.delete(product.id)
            products.removeAll { $0.id == product.id }
        } catch {
            errorMessage = "Delete failed: \\(error.localizedDescription)"
        }
    }
}

struct ProductListView: View {
    @State private var viewModel = ProductListViewModel()

    var body: some View {
        NavigationStack {
            Group {
                if viewModel.isLoading {
                    ProgressView("Loading...")
                } else {
                    List(viewModel.filteredProducts) { product in
                        ProductRow(product: product)
                    }
                    .searchable(text: $viewModel.searchText)
                }
            }
            .navigationTitle("Products")
        }
        .task { await viewModel.loadProducts() }
        .alert("Error", isPresented: .constant(viewModel.errorMessage != nil)) {
            Button("OK") { viewModel.errorMessage = nil }
        } message: {
            Text(viewModel.errorMessage ?? "")
        }
    }
}

// TCA - Product list
import ComposableArchitecture
import SwiftUI

@Reducer
struct ProductListFeature {
    @ObservableState
    struct State: Equatable {
        var products: [Product] = []
        var isLoading = false
        var errorMessage: String?
        var searchText = ""

        var filteredProducts: [Product] {
            guard !searchText.isEmpty else { return products }
            return products.filter { $0.name.localizedCaseInsensitiveContains(searchText) }
        }
    }

    enum Action {
        case onAppear
        case searchTextChanged(String)
        case deleteProduct(id: String)
        case productsLoaded(Result<[Product], Error>)
        case productDeleted(Result<Void, Error>)
        case dismissError
    }

    @Dependency(\\.productRepository) var repository

    var body: some ReducerOf<Self> {
        Reduce { state, action in
            switch action {
            case .onAppear:
                state.isLoading = true
                return .run { send in
                    await send(.productsLoaded(
                        Result { try await repository.fetchProducts() }
                    ))
                }

            case .searchTextChanged(let text):
                state.searchText = text
                return .none

            case .deleteProduct(let id):
                return .run { send in
                    await send(.productDeleted(
                        Result { try await repository.delete(id) }
                    ))
                }

            case .productsLoaded(.success(let products)):
                state.isLoading = false
                state.products = products
                return .none

            case .productsLoaded(.failure(let error)):
                state.isLoading = false
                state.errorMessage = error.localizedDescription
                return .none

            case .productDeleted(.success):
                return .send(.onAppear)

            case .productDeleted(.failure(let error)):
                state.errorMessage = error.localizedDescription
                return .none

            case .dismissError:
                state.errorMessage = nil
                return .none
            }
        }
    }
}

struct ProductListView: View {
    let store: StoreOf<ProductListFeature>

    var body: some View {
        WithPerceptionTracking {
            NavigationStack {
                List(store.filteredProducts) { product in
                    Text(product.name)
                }
                .searchable(text: store.binding(get: \\.searchText, send: ProductListFeature.Action.searchTextChanged))
                .navigationTitle("Products")
            }
            .task { store.send(.onAppear) }
        }
    }
}