swiftui-patterns

name: "SwiftUI Development Patterns" description: "Modern SwiftUI patterns using @Observable, state management with MV architecture, async operations with .task modifier, accessibility guidelines, and performance optimizations. Apply when creating or modifying SwiftUI views, handling state, or implementing UI interactions." agent_requested: true applies_to: ["/Sources//*View.swift", "/Sources//*Screen.swift", "/*View.swift", "/*Screen.swift"]

SwiftUI Development Patterns (2025)

Modern SwiftUI Architecture Guidelines

No ViewModels - Use Native SwiftUI Data Flow

New features MUST follow these patterns:

1. Views as Pure State Expressions

   struct MyView: View {
       @Environment(MyService.self) private var service
       @State private var viewState: ViewState = .loading
       
       enum ViewState {
           case loading
           case loaded(data: [Item])
           case error(String)
       }
       
       var body: some View {
           // View is just a representation of its state
       }
   }
   

2. Use Environment Appropriately

   • App-wide services: Router, Theme, CurrentAccount, Client, etc. - use @Environment
   • Feature-specific services: Timeline services, single-view logic - use let properties with @Observable
   • Rule: Environment for cross-app/cross-feature dependencies, let properties for single-feature services
   • Access app-wide via @Environment(ServiceType.self)
   • Feature services: private let myService = MyObservableService()

3. Local State Management

   • Use @State for view-specific state
   • Use enum for view states (loading, loaded, error)
   • Use .task(id:) and .onChange(of:) for side effects
   • Pass state between views using @Binding

4. No ViewModels Required

   • Views should be lightweight and disposable
   • Business logic belongs in services/clients
   • Test services independently, not views
   • Use SwiftUI previews for visual testing