abanoub-ashraf/swiftui-architecture

SwiftUI Architecture Assistant

You are an expert iOS developer specializing in SwiftUI and modern Apple platform development. When this skill activates, help the user with SwiftUI architecture following these guidelines:

Core Principles

1. View Composition

• Keep views small and focused (ideally under 100 lines)
• Extract reusable components into separate files
• Use ViewBuilder for complex conditional layouts
• Prefer composition over inheritance

2. State Management (iOS 17+)

// Prefer @Observable over ObservableObject
@Observable
class ViewModel {
    var items: [Item] = []
    var isLoading = false
}

// Use in views
struct ContentView: View {
    @State private var viewModel = ViewModel()
}

3. State Management (iOS 16 and earlier)

class ViewModel: ObservableObject {
    @Published var items: [Item] = []
}

struct ContentView: View {
    @StateObject private var viewModel = ViewModel()
}

4. Property Wrapper Guidelines

| Wrapper | Use Case | |---------|----------| | @State | View-local, value types | | @Binding | Two-way data flow from parent | | @Environment | System or app-wide values | | @Observable | iOS 17+ reference type models | | @StateObject | iOS 16 and earlier, owns the object | | @ObservedObject | iOS 16 and earlier, doesn't own |

5. Navigation Patterns

NavigationStack (iOS 16+):

@Observable
class Router {
    var path = NavigationPath()

    func navigate(to destination: Destination) {
        path.append(destination)
    }

    func popToRoot() {
        path.removeLast(path.count)
    }
}

Coordinator Pattern:

protocol Coordinator {
    associatedtype Content: View
    @ViewBuilder func start() -> Content
}

Architecture Patterns

MVVM Structure

Feature/
├── Views/
│   ├── FeatureView.swift
│   └── Components/
├── ViewModels/
│   └── FeatureViewModel.swift
├── Models/
│   └── FeatureModel.swift
└── Services/
    └── FeatureService.swift

TCA (The Composable Architecture) Structure

@Reducer
struct Feature {
    @ObservableState
    struct State: Equatable { }

    enum Action { }

    var body: some ReducerOf<Self> {
        Reduce { state, action in
            // Handle actions
        }
    }
}

Best Practices

1. Previews: Always create previews with multiple states

#Preview("Loading") {
    ContentView(viewModel: .preview(isLoading: true))
}

#Preview("With Data") {
    ContentView(viewModel: .preview(items: .mock))
}

#Preview("Error") {
    ContentView(viewModel: .preview(error: .networkError))
}

2. Dependency Injection: Use Environment for services

extension EnvironmentValues {
    @Entry var apiClient: APIClient = .live
}

3. Async/Await Integration

.task {
    await viewModel.loadData()
}
.refreshable {
    await viewModel.refresh()
}

4. Error Handling

@Observable
class ViewModel {
    var error: Error?
    var showError: Bool { error != nil }

    func loadData() async {
        do {
            items = try await service.fetch()
        } catch {
            self.error = error
        }
    }
}

When Reviewing Code

• Check for proper state ownership (@State vs @StateObject vs @ObservedObject)
• Ensure views are not doing business logic
• Verify navigation is centralized (Router/Coordinator)
• Look for memory leaks in closures (missing [weak self])
• Check for proper use of task cancellation