IOS Swift Patterns

iOS Swift Patterns

Production-grade iOS development with Swift, SwiftUI, and UIKit.

Architecture

MVVM + Coordinator Pattern

View (SwiftUI/UIViewController)
  ↕ binds to
ViewModel (ObservableObject)
  ↕ calls
Service Layer (Networking, DB)
  ↕
Core Data / API

Key Principles

• Views are dumb: They render state and forward actions — no business logic
• ViewModels own state: @Published properties, @State only for local UI
• Services are stateless: Network calls, DB operations, analytics
• Coordinators handle navigation: Removing navigation from views makes them reusable

SwiftUI Best Practices

Performance

• Use LazyVStack/LazyHStack for large lists, not VStack
• Mark views with @MainActor explicitly
• Use equatable() on complex views to prevent unnecessary re-renders
• Prefer @State for local, @StateObject for owned, @ObservedObject for passed-in

State Management

// Good: Clear separation
@MainActor
class UserViewModel: ObservableObject {
    @Published var users: [User] = []
    @Published var isLoading = false

    func loadUsers() async {
        isLoading = true
        users = await userService.fetchUsers()
        isLoading = false
    }
}

App Store Submission Checklist

• No Hardcoded API keys
• TestFlight beta tested with real users
• Privacy manifest updated
• Screenshots for all required sizes
• App Store description and keywords ready
• Subscription/IAP products configured

Source: cosmicstack-labs/mercury-agent-skills — distributed by TomeVault.