iOS Reviewer Skill

Purpose

Reviews iOS Swift code for SwiftUI, UIKit, Combine, and Swift Concurrency best practices.

When to Use

• iOS Swift project code review
• "SwiftUI", "UIKit", "Combine", "async/await" mentions
• iOS performance, memory management inspection
• Projects with .xcodeproj or .xcworkspace

Project Detection

• .xcodeproj or .xcworkspace exists
• Package.swift with iOS platform
• Info.plist exists
• *.swift files present

Workflow

Step 1: Analyze Project

**Swift**: 5.9+
**iOS Target**: 15.0+
**UI Framework**: SwiftUI / UIKit
**Architecture**: MVVM / TCA / Clean Architecture
**Package Manager**: SPM / CocoaPods / Carthage

Step 2: Select Review Areas

AskUserQuestion:

"Which areas to review?"
Options:
- Full iOS pattern check (recommended)
- SwiftUI view patterns
- UIKit lifecycle/memory
- Combine/async-await usage
- Architecture patterns
multiSelect: true

Detection Rules

SwiftUI Patterns

Check	Recommendation	Severity
Heavy computation in body	Move to ViewModel or task modifier	HIGH
Missing @State/@StateObject distinction	Use @StateObject for owned objects	HIGH
ObservableObject without @Published	Add @Published to observed properties	HIGH
Missing EnvironmentObject injection	Ensure parent provides object	MEDIUM
Large View body	Extract to smaller Views	MEDIUM

// BAD: Heavy computation in body
struct MyView: View {
    var body: some View {
        let result = expensiveCalculation()  // Called every render
        Text(result)
    }
}

// GOOD: Move to ViewModel or use task
struct MyView: View {
    @StateObject var viewModel = MyViewModel()
    var body: some View {
        Text(viewModel.result)
            .task { await viewModel.calculate() }
    }
}

// BAD: @State for reference type
struct MyView: View {
    @State var viewModel = MyViewModel()  // Won't observe changes
}

// GOOD: @StateObject for reference type
struct MyView: View {
    @StateObject var viewModel = MyViewModel()
}

// BAD: Missing @Published
class MyViewModel: ObservableObject {
    var data: [String] = []  // Changes won't trigger view update
}

// GOOD: Add @Published
class MyViewModel: ObservableObject {
    @Published var data: [String] = []
}

UIKit Patterns

Check	Issue	Severity
Strong delegate reference	Retain cycle risk	CRITICAL
Missing removeObserver	Memory leak	HIGH
Force unwrap IBOutlet	Crash risk	HIGH
viewDidLoad network call	UX issue	MEDIUM
Main thread UI update missing	Undefined behavior	CRITICAL

// BAD: Strong delegate
class MyViewController: UIViewController {
    var delegate: MyDelegate?  // Strong reference!
}

// GOOD: Weak delegate
class MyViewController: UIViewController {
    weak var delegate: MyDelegate?
}

// BAD: Missing removeObserver
override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, ...)
}

// GOOD: Remove in deinit
deinit {
    NotificationCenter.default.removeObserver(self)
}

// BAD: Force unwrap IBOutlet
@IBOutlet var titleLabel: UILabel!
func setup() {
    titleLabel.text = "Hello"  // Crash if not connected
}

// GOOD: Safe unwrap
@IBOutlet weak var titleLabel: UILabel?
func setup() {
    titleLabel?.text = "Hello"
}

Combine Patterns

Check	Recommendation	Severity
Missing store in cancellables	Subscription lost	CRITICAL
receive(on:) missing for UI	Threading issue	HIGH
PassthroughSubject without type erasure	Exposes implementation	MEDIUM
Chain without error handling	Silent failures	MEDIUM

// BAD: Missing store
class MyViewModel {
    func subscribe() {
        publisher.sink { value in
            print(value)
        }  // Immediately cancelled!
    }
}

// GOOD: Store in cancellables
class MyViewModel {
    private var cancellables = Set<AnyCancellable>()

    func subscribe() {
        publisher
            .sink { value in print(value) }
            .store(in: &cancellables)
    }
}

// BAD: Missing receive(on:) for UI
publisher
    .sink { self.label.text = $0 }  // May not be on main thread
    .store(in: &cancellables)

// GOOD: Explicit main thread
publisher
    .receive(on: DispatchQueue.main)
    .sink { self.label.text = $0 }
    .store(in: &cancellables)

Swift Concurrency (async/await)

Check	Recommendation	Severity
Blocking call in async context	Use async alternative	HIGH
Missing @MainActor for UI	Threading issue	HIGH
Task without cancellation handling	Resource leak	MEDIUM
Unstructured Task in SwiftUI	Use .task modifier	MEDIUM

// BAD: Blocking in async
func fetchData() async -> Data {
    return URLSession.shared.dataTask(...)  // Blocking!
}

// GOOD: Async alternative
func fetchData() async throws -> Data {
    let (data, _) = try await URLSession.shared.data(from: url)
    return data
}

// BAD: Missing @MainActor for UI
class MyViewModel: ObservableObject {
    @Published var items: [Item] = []

    func load() async {
        items = await fetchItems()  // May not be on main thread!
    }
}

// GOOD: @MainActor
@MainActor
class MyViewModel: ObservableObject {
    @Published var items: [Item] = []

    func load() async {
        items = await fetchItems()  // Guaranteed main thread
    }
}

// BAD: Unstructured Task in SwiftUI
struct MyView: View {
    var body: some View {
        Text("Hello")
            .onAppear {
                Task { await load() }  // Not cancelled on disappear
            }
    }
}

// GOOD: Use .task modifier
struct MyView: View {
    var body: some View {
        Text("Hello")
            .task { await load() }  // Auto-cancelled
    }
}

Memory Management

Check	Problem	Solution
Strong self in closure	Retain cycle	[weak self] or [unowned self]
Circular reference	Memory leak	Break cycle with weak
Large image in memory	OOM risk	Use thumbnails, purge cache
Uncancelled Task	Resource leak	Store and cancel

// BAD: Strong self in closure
class MyViewController: UIViewController {
    func setup() {
        service.fetch { result in
            self.update(result)  // Strong capture!
        }
    }
}

// GOOD: Weak self
class MyViewController: UIViewController {
    func setup() {
        service.fetch { [weak self] result in
            self?.update(result)
        }
    }
}

Response Template

## iOS Code Review Results

**Project**: [name]
**Swift**: 5.9 | **iOS Target**: 15.0+
**UI Framework**: SwiftUI/UIKit
**Files Analyzed**: X

### SwiftUI Patterns
| Status | File | Issue |
|--------|------|-------|
| HIGH | Views/HomeView.swift | Heavy computation in body (line 45) |
| MEDIUM | Views/ProfileView.swift | Large view body, extract components |

### UIKit/Memory
| Status | File | Issue |
|--------|------|-------|
| CRITICAL | Controllers/DetailVC.swift | Strong delegate reference (line 23) |
| HIGH | Controllers/ListVC.swift | Missing removeObserver in deinit |

### Combine/Async
| Status | File | Issue |
|--------|------|-------|
| CRITICAL | Services/DataService.swift | Missing cancellable store |
| HIGH | ViewModels/MainVM.swift | Missing @MainActor |

### Recommended Actions
1. [ ] Add [weak self] to closures
2. [ ] Use @StateObject for owned ObservableObjects
3. [ ] Add @MainActor to ViewModels
4. [ ] Replace Task with .task modifier

Best Practices

1. SwiftUI: Prefer small, composable Views with proper state ownership
2. UIKit: Always use weak delegates, clean up observers
3. Combine: Store subscriptions, handle threading explicitly
4. Concurrency: Use structured concurrency, @MainActor for UI
5. Memory: Use weak captures, profile with Instruments

Integration

• code-reviewer skill: General Swift code quality
• test-generator skill: iOS XCTest generation
• security-scanner skill: iOS security checks

Notes

• Based on Swift 5.9+, iOS 15+
• Supports SwiftUI and UIKit projects
• Includes Swift Concurrency patterns (async/await)