iOS State Management Standards

Priority: P0

Implementation Guidelines

Combine (Reactive States)

• Publishers: Use

  @Published

  for standard state in ViewModels. Use

  PassthroughSubject

  for one-time navigation or alert events.
• Memory Management: Store subscriptions in a

  Set<AnyCancellable>

  . Use

  .store(in: &cancellables)

  to prevent memory leaks and ensure they are cleared on deinit.
• Operators: Use specific operators like

  .debounce

  ,

  .filter

  ,

  .map

  , and

  .flatMap

  to handle complex input streams.
• Schedulers: Always ensure UI property updates occur on the main thread using

  @MainActor

  or

  .receive(on: DispatchQueue.main)

  .

Observation Framework (iOS 17+)

• @Observable

  : Use the

  @Observable

  macro for modern, high-performance observation in SwiftUI.
• State Properties: In SwiftUI views, use

  @Bindable

  for two-way bindings with

  @Observable

  objects.
• Namespaces: Use

  @Namespace

  for match-geometry animations and coordinate space tracking.

Unidirectional Data Flow (UDF)

• Input/Output: ViewModels should expose an

  Input

  enum (events) and

  Output

  struct (state) to enforce a clear data direction.
• ViewState: Prefer a single, exhaustive

  ViewState

  enum (e.g.,

  .loading

  ,

  .success(data)

  ,

  .error(failure)

  ).

Anti-Patterns

• No uncleared subscriptions: Always use .store(in: &cancellables).
• No UI updates on background: Use .receive(on: .main).
• No manual objectWillChange: Use @Published or @Observable.

References

• Combine & Observation Setup