Introduction

SwiftUI's simplicity is both its greatest strength and biggest trap. @State, @Binding, and simple views work great for tutorials, but they fall apart in production apps with complex state, networking, and business logic. This guide covers the architecture patterns that scale.

The Problem with Simple Patterns

Most SwiftUI tutorials show code like this:

struct ContentView: View {
    @State private var items: [Item] = []
    @State private var isLoading = false
    
    var body: some View {
        List(items) { item in
            Text(item.name)
        }
        .onAppear {
            loadItems()
        }
    }
}

This breaks down when you need shared state, complex business logic, testable code, and proper error handling.

Pattern 1: MVVM with ObservableObject

The most common pattern for medium-to-large SwiftUI apps:

class ItemListViewModel: ObservableObject {
    @Published var items: [Item] = []
    @Published var isLoading = false
    @Published var error: Error?
    
    private let repository: ItemRepository
    
    init(repository: ItemRepository = ItemRepository()) {
        self.repository = repository
    }
    
    func loadItems() {
        isLoading = true
        // fetch logic...
    }
}

Pattern 2: Repository Pattern for Data Layer

Never put networking code directly in ViewModels. Use a repository to centralize data access logic, add caching, and make it mockable for testing.

Pattern 3: Coordinator Pattern for Navigation

Don't let views manage navigation. Use a coordinator with NavigationPath to centralize navigation logic and support deep linking.

Conclusion

SwiftUI's declarative nature doesn't mean you should skip architecture. These patterns have proven effective in production apps ranging from 50K to 500K lines of code. Start with MVVM and Repository, then add Coordinator and DI as your app grows.

What architecture patterns are you using in your SwiftUI apps? Let me know in the comments!