ios-development

iOS Development Skill

Quick orientation

Before anything else, identify:

1. UI framework → SwiftUI / UIKit / mixed?
2. Architecture → MVVM / TCA / VIPER / Clean / MVC?
3. iOS target → iOS 16 / 17 / 18? (affects API availability)
4. Task type → new feature / debug / refactor / architecture / performance / release?
5. Graphics intensity → стандартный UI / средняя 3D / тяжёлая графика / Metal?

Если задача связана с Metal, GPU, рендерингом, шейдерами, TBDR, MetalFX, GPU profiling, frame pacing, PSO, heaps, ICB, MTLIO → читать references/metal-graphics.md первым.

Then read the relevant reference file before writing code.

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Reference files — read when needed

Topic	File	When to read
SwiftUI pipeline	references/swiftui.md	SwiftUI views, state, bindings, modifiers, animations
UIKit pipeline	references/uikit.md	UIViewController, Auto Layout, delegates, storyboards
Architecture	references/architecture.md	MVVM, TCA, VIPER, Clean, Coordinator
Networking	references/networking.md	URLSession, async/await, REST/GraphQL, auth
Data persistence	references/data.md	CoreData, SwiftData, UserDefaults, Keychain, FileManager
Navigation	references/navigation.md	NavigationStack, Coordinator, deep links, sheets
Performance	references/performance.md	Instruments, memory, launch time, rendering
Metal & Heavy Graphics	references/metal-graphics.md	Metal, GPU рендер, TBDR, PSO/heaps/argument buffers, ICB, MTLIO, MetalFX, терморегуляция, профилирование GPU

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iOS version matrix (API availability)

Feature	Min iOS
SwiftUI	iOS 13
async/await	iOS 15
NavigationStack	iOS 16
SwiftData	iOS 17
@Observable macro	iOS 17
RippleEffect, ScrollView phases	iOS 18

Always check target before using newer APIs. Use #available guards for backward compatibility:

if #available(iOS 17, *) {
    // SwiftData or @Observable
} else {
    // fallback
}

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Core Swift patterns (always apply)

Concurrency — async/await first

// Prefer this
func loadUser() async throws -> User {
    let data = try await URLSession.shared.data(from: url).0
    return try JSONDecoder().decode(User.self, from: data)
}

// Call site
Task {
    do {
        user = try await loadUser()
    } catch {
        errorMessage = error.localizedDescription
    }
}

Error handling — typed errors

enum AppError: LocalizedError {
    case networkUnavailable
    case decodingFailed(String)
    case unauthorized
    
    var errorDescription: String? {
        switch self {
        case .networkUnavailable: return "No internet connection"
        case .decodingFailed(let detail): return "Data error: \(detail)"
        case .unauthorized: return "Please sign in again"
        }
    }
}

Value types first

Prefer struct over class unless you need reference semantics, inheritance, or @Observable.

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Architecture decision tree

Is the screen purely data-display with simple interaction?
  YES → MVC / simple SwiftUI View with @State is fine
  NO ↓

Is business logic testable without UI?
  Required → use ViewModel (MVVM) or Store (TCA)

Is navigation/routing complex (deep links, coordinator)?
  YES → read references/navigation.md → Coordinator pattern

Is the team large or is this a long-lived product?
  YES → Clean Architecture or TCA → read references/architecture.md

Default for most apps: MVVM + Coordinator

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State management quick reference

SwiftUI state hierarchy

Local transient state       → @State
Passed from parent          → @Binding
Shared across views         → @StateObject / @ObservedObject (iOS 16-)
                            → @State with @Observable class (iOS 17+)
App-wide environment        → @EnvironmentObject / @Environment

iOS 17+ preferred (@Observable)

@Observable
class UserStore {
    var users: [User] = []
    var isLoading = false
}

// In View — no property wrapper needed
struct UserListView: View {
    var store: UserStore  // just pass it
    var body: some View {
        List(store.users) { Text($0.name) }
    }
}

iOS 16 and below (ObservableObject)

class UserViewModel: ObservableObject {
    @Published var users: [User] = []
    @Published var isLoading = false
}

struct UserListView: View {
    @StateObject private var vm = UserViewModel()
}

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Xcode & project setup checklist

New project:

• Set deployment target explicitly
• Enable Swift strict concurrency warnings (SWIFT_STRICT_CONCURRENCY = complete)
• Add .gitignore for Xcode (xcuserdata, DerivedData)
• Configure signing (automatic vs manual)
• Set bundle ID and version/build numbers

Capabilities to enable when needed:

• Push Notifications → add Push Notifications capability
• Background fetch → Background Modes
• iCloud/CloudKit → iCloud
• Sign in with Apple → Sign In with Apple

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Testing baseline

// Unit test — ViewModel
@MainActor
final class UserViewModelTests: XCTestCase {
    func testLoadUsers() async throws {
        let vm = UserViewModel(service: MockUserService())
        await vm.loadUsers()
        XCTAssertFalse(vm.users.isEmpty)
    }
}

// UI test — basic
func testLoginFlow() {
    let app = XCUIApplication()
    app.launch()
    app.textFields["Email"].tap()
    app.textFields["Email"].typeText("[email protected]")
    app.buttons["Continue"].tap()
    XCTAssertTrue(app.navigationBars["Home"].exists)
}

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Common pitfalls

Pitfall	Fix
Purple warning: "Publishing changes from background thread"	Wrap in await MainActor.run { } or mark func @MainActor
View re-renders too often	Audit @State/@Published — split large ViewModels
Memory leak in closures	Use [weak self] captures in escaping closures
@StateObject recreated	Move object creation up the tree; don't init in body
Keyboard covering text field	Use .ignoresSafeArea(.keyboard, edges: .bottom) or ScrollView
Slow list	Use LazyVStack or List with id: stability
Simulator ≠ device behavior	Always test on real device before submission
Metal: CPU↔GPU stall	Triple buffer + DispatchSemaphore; никогда не ждать GPU синхронно в draw()
Metal: PSO компилируется в рантайме	Создавать все PSO до первого кадра, кешировать
Metal: лишние load/store	storeAction = .dontCare для transient (depth buffer)
Metal: OOM jetsam	Мониторить currentAllocatedSize vs recommendedMaxWorkingSetSize; освобождать при warning
Metal: статтер при загрузке	MTLIO + MTLSharedEvent вместо блокирующей загрузки; ODR для тяжёлых ассетов
Metal: перегрев	Подписаться на thermalStateDidChangeNotification, адаптировать render scale + FPS

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Hardware budget ориентиры (GPU capability levels)

Планировать по capability-уровням, не под конкретную модель. Всегда включать adaptive quality.

Уровень	SoC	Реалистичный target	Ключевые ограничения
Широкий охват	A13–A15 (iPhone SE, 13, 14)	30–60 FPS, агрессивный render scale	Строгий бюджет RT; MetalFX обязателен для сложных сцен
Средний	A16 (iPhone 15), M1	60 FPS при хорошем пайплайне	MetalFX + динамический render scale
Флагман	A17 Pro (iPhone 15 Pro), M3+	60–120 FPS, тяжёлые эффекты	Ray tracing (аппаратный); всё равно нужен thermal management

Важно: даже флагманы упираются в термальную стабильность при длительной нагрузке, а не в пиковую мощность GPU.

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App Store submission checklist

• Increment build number for every TestFlight upload
• Privacy manifest (PrivacyInfo.xcprivacy) required for sensitive APIs
• App icons all sizes provided (use Asset Catalog)
• Screenshots for all required device sizes
• Export compliance (encryption questions)
• App Review Information filled in
• No UIRequiresFullScreen = NO without iPad support reasoning