iOS Knowledge Skill – Architecture & Patterns

This skill equips agents with high-level iOS knowledge for the OS 4.1 iOS lane without bloating individual agent prompts.

It is intended for:

• ios-grand-architect
• ios-architect
• Core iOS specialists (SwiftUI/UIKit/persistence/networking/testing/perf/security) when they need architectural context.

Context7 Libraries

When you load this skill, you MAY use context7 MCP tools to read from:

• os2-ios-architecture

  • SwiftUI vs UIKit vs mixed stack guidance,
  • MVVM/TCA/Clean patterns for iOS,
  • Navigation, modularization, and dependency injection strategies.

• os2-ios-standards

  • Coding standards for the iOS lane,
  • Error handling and logging patterns,
  • Guidelines for concurrency, testing, and app structure.

• /websites/developer_apple_swiftdata (via Context7)

  • SwiftData models with @Model, @Relationship, cascade deletes
  • Preferred over Core Data for iOS 17.0+ projects
  • In-memory testing with ModelContainer
  • Native, zero-dependency persistence

• /ra1028/swiftui-atom-properties (via Context7)

  • Atomic state management for complex cross-feature coordination
  • StateAtom, ValueAtom, ObservableObjectAtom patterns
  • Testing with AtomTestContext
  • Compile-safe dependency injection

• /pointfreeco/swift-navigation (via Context7)

  • State-driven navigation with @CasePathable enums
  • Sheet/modal presentation tied to model state
  • Deep linking and state restoration
  • Two-way bindings for navigation state

You SHOULD:

• Read only the sections relevant to the current task,
• Summarize 3–7 key constraints or patterns into your own working context,
• Avoid loading large example sections unless explicitly needed.

Usage Pattern

1. When planning an iOS task:

   • Load ios-knowledge-skill and skim the relevant context7 docs.
   • Extract:
     • Recommended UI stack (SwiftUI vs UIKit/TCA/MVVM),
     • Data strategy hints (SwiftData vs Core Data/GRDB),
     • Lane-specific constraints (design DNA/tokens, concurrency rules).

2. When writing phase_state.planning:

   • Reflect these decisions in:
     • architecture_path,
     • data_strategy,
     • plan_summary.

3. When delegating to implementers/gates:

   • Ensure the plan and assignment reflect the chosen patterns,
   • Reference this skill implicitly (do not restate everything in agent prompts).

4. When planning data persistence (iOS 17.0+):

   • Prefer SwiftData with @Model macro for new projects
   • Use @Relationship(.cascade) for parent-child relationships
   • Plan ModelContainer with isStoredInMemoryOnly for testing
   • Consider SwiftData Query for reactive UI updates

5. When planning complex state management:

   • Consider SwiftUI Atom Properties for cross-feature state coordination
   • Use StateAtom for mutable state (replaces @State for shared state)
   • Use ValueAtom for computed/derived values
   • Use ObservableObjectAtom for complex objects
   • Plan AtomTestContext tests for state logic

6. When planning navigation architecture:

   • Consider Swift Navigation for state-driven navigation
   • Model destinations as @CasePathable enums
   • Tie sheet/modal/alert presentation to model state
   • Plan for deep linking via URL → destination state mapping
   • Use navigationDestination(item:) for push navigation

This skill is about progressive disclosure: give agents just enough iOS architecture knowledge to make good decisions, while leaving detailed examples and recipes in context7 where they can be fetched on demand.