# State Management

> iOS State Management Standards

- Skill: `fierzone/state-management-2` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add fierzone/state-management-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/fierzone/state-management-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: fierzone (https://skillmd.com/u/fierzone)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/fierzone/state-management-2

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# iOS State Management Standards

## **Priority: P0**

## Implementation Guidelines

### Combine (Reactive)

- **Publishers**: Use `@Published` for state in ViewModels. Use `PassthroughSubject` for one-time events (Transitions/Alerts).
- **Memory Management**: Store subscriptions in a `Set<AnyCancellable>`. Ensure they are cleared on deinit.
- **Operators**: Use operators like `.debounce`, `.filter`, `.map`, and `.flatMap` to transform input stream.
- **Schedulers**: Always prefix UI property updates with `@MainActor` or use `.receive(on: DispatchQueue.main)`.

### Observation Framework (iOS 17+)

- **@Observable**: Use for modern, macro-based observation. Replace `ObservableObject` in SwiftUI apps.
- **Binding**: Use `$state` for two-way bindings in SwiftUI. No boilerplate `objectWillChange` calls.

### Best Practices

- **ViewState Unification**: Prefer a single `State` enum or struct (Unidirectional) for complex screens.
- **Avoid Over-Reactive**: Don't use Combine for simple local flags. Use standard `@State` or variables.

## Anti-Patterns

- **Subscription Leaks**: `**No uncleared subscriptions**: Always use .store(in: &cancellables).`
- **Main Thread Violation**: `**No UI updates on Background**: Use .receive(on: .main).`
- **Manual objectWillChange**: `**No manual notifications**: Use @Published or @Observable.`

## References

- [Combine & Observation Setup](references/implementation.md)