Merge pull request #244 from maxdimitrov/feat/rules/swift

LGTM — Swift rules and SwiftUI patterns skill. Pure documentation, no security concerns.

rules/README.md

@@ -16,7 +16,8 @@ rules/
 │   └── security.md
 ├── typescript/      # TypeScript/JavaScript specific
 ├── python/          # Python specific
-└── golang/          # Go specific
+├── golang/          # Go specific
+└── swift/           # Swift specific
 ```
 
 - **common/** contains universal principles — no language-specific code examples.
@@ -31,6 +32,7 @@ rules/
 ./install.sh typescript
 ./install.sh python
 ./install.sh golang
+./install.sh swift
 
 # Install multiple languages at once
 ./install.sh typescript python
@@ -52,6 +54,7 @@ cp -r rules/common ~/.claude/rules/common
 cp -r rules/typescript ~/.claude/rules/typescript
 cp -r rules/python ~/.claude/rules/python
 cp -r rules/golang ~/.claude/rules/golang
+cp -r rules/swift ~/.claude/rules/swift
 
 # Attention ! ! ! Configure according to your actual project requirements; the configuration here is for reference only.
 ```

rules/swift/coding-style.md

@@ -0,0 +1,47 @@
+---
+paths:
+  - "**/*.swift"
+  - "**/Package.swift"
+---
+# Swift Coding Style
+
+> This file extends [common/coding-style.md](../common/coding-style.md) with Swift specific content.
+
+## Formatting
+
+- **SwiftFormat** for auto-formatting, **SwiftLint** for style enforcement
+- `swift-format` is bundled with Xcode 16+ as an alternative
+
+## Immutability
+
+- Prefer `let` over `var` — define everything as `let` and only change to `var` if the compiler requires it
+- Use `struct` with value semantics by default; use `class` only when identity or reference semantics are needed
+
+## Naming
+
+Follow [Apple API Design Guidelines](https://www.swift.org/documentation/api-design-guidelines/):
+
+- Clarity at the point of use — omit needless words
+- Name methods and properties for their roles, not their types
+- Use `static let` for constants over global constants
+
+## Error Handling
+
+Use typed throws (Swift 6+) and pattern matching:
+
+```swift
+func load(id: String) throws(LoadError) -> Item {
+    guard let data = try? read(from: path) else {
+        throw .fileNotFound(id)
+    }
+    return try decode(data)
+}
+```
+
+## Concurrency
+
+Enable Swift 6 strict concurrency checking. Prefer:
+
+- `Sendable` value types for data crossing isolation boundaries
+- Actors for shared mutable state
+- Structured concurrency (`async let`, `TaskGroup`) over unstructured `Task {}`

rules/swift/hooks.md

@@ -0,0 +1,20 @@
+---
+paths:
+  - "**/*.swift"
+  - "**/Package.swift"
+---
+# Swift Hooks
+
+> This file extends [common/hooks.md](../common/hooks.md) with Swift specific content.
+
+## PostToolUse Hooks
+
+Configure in `~/.claude/settings.json`:
+
+- **SwiftFormat**: Auto-format `.swift` files after edit
+- **SwiftLint**: Run lint checks after editing `.swift` files
+- **swift build**: Type-check modified packages after edit
+
+## Warning
+
+Flag `print()` statements — use `os.Logger` or structured logging instead for production code.

rules/swift/patterns.md

@@ -0,0 +1,66 @@
+---
+paths:
+  - "**/*.swift"
+  - "**/Package.swift"
+---
+# Swift Patterns
+
+> This file extends [common/patterns.md](../common/patterns.md) with Swift specific content.
+
+## Protocol-Oriented Design
+
+Define small, focused protocols. Use protocol extensions for shared defaults:
+
+```swift
+protocol Repository: Sendable {
+    associatedtype Item: Identifiable & Sendable
+    func find(by id: Item.ID) async throws -> Item?
+    func save(_ item: Item) async throws
+}
+```
+
+## Value Types
+
+- Use structs for data transfer objects and models
+- Use enums with associated values to model distinct states:
+
+```swift
+enum LoadState<T: Sendable>: Sendable {
+    case idle
+    case loading
+    case loaded(T)
+    case failed(Error)
+}
+```
+
+## Actor Pattern
+
+Use actors for shared mutable state instead of locks or dispatch queues:
+
+```swift
+actor Cache<Key: Hashable & Sendable, Value: Sendable> {
+    private var storage: [Key: Value] = [:]
+
+    func get(_ key: Key) -> Value? { storage[key] }
+    func set(_ key: Key, value: Value) { storage[key] = value }
+}
+```
+
+## Dependency Injection
+
+Inject protocols with default parameters — production uses defaults, tests inject mocks:
+
+```swift
+struct UserService {
+    private let repository: any UserRepository
+
+    init(repository: any UserRepository = DefaultUserRepository()) {
+        self.repository = repository
+    }
+}
+```
+
+## References
+
+See skill: `swift-actor-persistence` for actor-based persistence patterns.
+See skill: `swift-protocol-di-testing` for protocol-based DI and testing.

rules/swift/security.md

@@ -0,0 +1,33 @@
+---
+paths:
+  - "**/*.swift"
+  - "**/Package.swift"
+---
+# Swift Security
+
+> This file extends [common/security.md](../common/security.md) with Swift specific content.
+
+## Secret Management
+
+- Use **Keychain Services** for sensitive data (tokens, passwords, keys) — never `UserDefaults`
+- Use environment variables or `.xcconfig` files for build-time secrets
+- Never hardcode secrets in source — decompilation tools extract them trivially
+
+```swift
+let apiKey = ProcessInfo.processInfo.environment["API_KEY"]
+guard let apiKey, !apiKey.isEmpty else {
+    fatalError("API_KEY not configured")
+}
+```
+
+## Transport Security
+
+- App Transport Security (ATS) is enforced by default — do not disable it
+- Use certificate pinning for critical endpoints
+- Validate all server certificates
+
+## Input Validation
+
+- Sanitize all user input before display to prevent injection
+- Use `URL(string:)` with validation rather than force-unwrapping
+- Validate data from external sources (APIs, deep links, pasteboard) before processing

rules/swift/testing.md

@@ -0,0 +1,45 @@
+---
+paths:
+  - "**/*.swift"
+  - "**/Package.swift"
+---
+# Swift Testing
+
+> This file extends [common/testing.md](../common/testing.md) with Swift specific content.
+
+## Framework
+
+Use **Swift Testing** (`import Testing`) for new tests. Use `@Test` and `#expect`:
+
+```swift
+@Test("User creation validates email")
+func userCreationValidatesEmail() throws {
+    #expect(throws: ValidationError.invalidEmail) {
+        try User(email: "not-an-email")
+    }
+}
+```
+
+## Test Isolation
+
+Each test gets a fresh instance — set up in `init`, tear down in `deinit`. No shared mutable state between tests.
+
+## Parameterized Tests
+
+```swift
+@Test("Validates formats", arguments: ["json", "xml", "csv"])
+func validatesFormat(format: String) throws {
+    let parser = try Parser(format: format)
+    #expect(parser.isValid)
+}
+```
+
+## Coverage
+
+```bash
+swift test --enable-code-coverage
+```
+
+## Reference
+
+See skill: `swift-protocol-di-testing` for protocol-based dependency injection and mock patterns with Swift Testing.

skills/swiftui-patterns/SKILL.md

@@ -0,0 +1,259 @@
+---
+name: swiftui-patterns
+description: SwiftUI architecture patterns, state management with @Observable, view composition, navigation, performance optimization, and modern iOS/macOS UI best practices.
+---
+
+# SwiftUI Patterns
+
+Modern SwiftUI patterns for building declarative, performant user interfaces on Apple platforms. Covers the Observation framework, view composition, type-safe navigation, and performance optimization.
+
+## When to Activate
+
+- Building SwiftUI views and managing state (`@State`, `@Observable`, `@Binding`)
+- Designing navigation flows with `NavigationStack`
+- Structuring view models and data flow
+- Optimizing rendering performance for lists and complex layouts
+- Working with environment values and dependency injection in SwiftUI
+
+## State Management
+
+### Property Wrapper Selection
+
+Choose the simplest wrapper that fits:
+
+| Wrapper | Use Case |
+|---------|----------|
+| `@State` | View-local value types (toggles, form fields, sheet presentation) |
+| `@Binding` | Two-way reference to parent's `@State` |
+| `@Observable` class + `@State` | Owned model with multiple properties |
+| `@Observable` class (no wrapper) | Read-only reference passed from parent |
+| `@Bindable` | Two-way binding to an `@Observable` property |
+| `@Environment` | Shared dependencies injected via `.environment()` |
+
+### @Observable ViewModel
+
+Use `@Observable` (not `ObservableObject`) — it tracks property-level changes so SwiftUI only re-renders views that read the changed property:
+
+```swift
+@Observable
+final class ItemListViewModel {
+    private(set) var items: [Item] = []
+    private(set) var isLoading = false
+    var searchText = ""
+
+    private let repository: any ItemRepository
+
+    init(repository: any ItemRepository = DefaultItemRepository()) {
+        self.repository = repository
+    }
+
+    func load() async {
+        isLoading = true
+        defer { isLoading = false }
+        items = (try? await repository.fetchAll()) ?? []
+    }
+}
+```
+
+### View Consuming the ViewModel
+
+```swift
+struct ItemListView: View {
+    @State private var viewModel: ItemListViewModel
+
+    init(viewModel: ItemListViewModel = ItemListViewModel()) {
+        _viewModel = State(initialValue: viewModel)
+    }
+
+    var body: some View {
+        List(viewModel.items) { item in
+            ItemRow(item: item)
+        }
+        .searchable(text: $viewModel.searchText)
+        .overlay { if viewModel.isLoading { ProgressView() } }
+        .task { await viewModel.load() }
+    }
+}
+```
+
+### Environment Injection
+
+Replace `@EnvironmentObject` with `@Environment`:
+
+```swift
+// Inject
+ContentView()
+    .environment(authManager)
+
+// Consume
+struct ProfileView: View {
+    @Environment(AuthManager.self) private var auth
+
+    var body: some View {
+        Text(auth.currentUser?.name ?? "Guest")
+    }
+}
+```
+
+## View Composition
+
+### Extract Subviews to Limit Invalidation
+
+Break views into small, focused structs. When state changes, only the subview reading that state re-renders:
+
+```swift
+struct OrderView: View {
+    @State private var viewModel = OrderViewModel()
+
+    var body: some View {
+        VStack {
+            OrderHeader(title: viewModel.title)
+            OrderItemList(items: viewModel.items)
+            OrderTotal(total: viewModel.total)
+        }
+    }
+}
+```
+
+### ViewModifier for Reusable Styling
+
+```swift
+struct CardModifier: ViewModifier {
+    func body(content: Content) -> some View {
+        content
+            .padding()
+            .background(.regularMaterial)
+            .clipShape(RoundedRectangle(cornerRadius: 12))
+    }
+}
+
+extension View {
+    func cardStyle() -> some View {
+        modifier(CardModifier())
+    }
+}
+```
+
+## Navigation
+
+### Type-Safe NavigationStack
+
+Use `NavigationStack` with `NavigationPath` for programmatic, type-safe routing:
+
+```swift
+@Observable
+final class Router {
+    var path = NavigationPath()
+
+    func navigate(to destination: Destination) {
+        path.append(destination)
+    }
+
+    func popToRoot() {
+        path = NavigationPath()
+    }
+}
+
+enum Destination: Hashable {
+    case detail(Item.ID)
+    case settings
+    case profile(User.ID)
+}
+
+struct RootView: View {
+    @State private var router = Router()
+
+    var body: some View {
+        NavigationStack(path: $router.path) {
+            HomeView()
+                .navigationDestination(for: Destination.self) { dest in
+                    switch dest {
+                    case .detail(let id): ItemDetailView(itemID: id)
+                    case .settings: SettingsView()
+                    case .profile(let id): ProfileView(userID: id)
+                    }
+                }
+        }
+        .environment(router)
+    }
+}
+```
+
+## Performance
+
+### Use Lazy Containers for Large Collections
+
+`LazyVStack` and `LazyHStack` create views only when visible:
+
+```swift
+ScrollView {
+    LazyVStack(spacing: 8) {
+        ForEach(items) { item in
+            ItemRow(item: item)
+        }
+    }
+}
+```
+
+### Stable Identifiers
+
+Always use stable, unique IDs in `ForEach` — avoid using array indices:
+
+```swift
+// Use Identifiable conformance or explicit id
+ForEach(items, id: \.stableID) { item in
+    ItemRow(item: item)
+}
+```
+
+### Avoid Expensive Work in body
+
+- Never perform I/O, network calls, or heavy computation inside `body`
+- Use `.task {}` for async work — it cancels automatically when the view disappears
+- Use `.sensoryFeedback()` and `.geometryGroup()` sparingly in scroll views
+- Minimize `.shadow()`, `.blur()`, and `.mask()` in lists — they trigger offscreen rendering
+
+### Equatable Conformance
+
+For views with expensive bodies, conform to `Equatable` to skip unnecessary re-renders:
+
+```swift
+struct ExpensiveChartView: View, Equatable {
+    let dataPoints: [DataPoint] // DataPoint must conform to Equatable
+
+    static func == (lhs: Self, rhs: Self) -> Bool {
+        lhs.dataPoints == rhs.dataPoints
+    }
+
+    var body: some View {
+        // Complex chart rendering
+    }
+}
+```
+
+## Previews
+
+Use `#Preview` macro with inline mock data for fast iteration:
+
+```swift
+#Preview("Empty state") {
+    ItemListView(viewModel: ItemListViewModel(repository: EmptyMockRepository()))
+}
+
+#Preview("Loaded") {
+    ItemListView(viewModel: ItemListViewModel(repository: PopulatedMockRepository()))
+}
+```
+
+## Anti-Patterns to Avoid
+
+- Using `ObservableObject` / `@Published` / `@StateObject` / `@EnvironmentObject` in new code — migrate to `@Observable`
+- Putting async work directly in `body` or `init` — use `.task {}` or explicit load methods
+- Creating view models as `@State` inside child views that don't own the data — pass from parent instead
+- Using `AnyView` type erasure — prefer `@ViewBuilder` or `Group` for conditional views
+- Ignoring `Sendable` requirements when passing data to/from actors
+
+## References
+
+See skill: `swift-actor-persistence` for actor-based persistence patterns.
+See skill: `swift-protocol-di-testing` for protocol-based DI and testing with Swift Testing.