Swift Dev

Swift Development Expert

Expert guidance for modern Swift development across all Apple platforms and server-side applications. Leverage idiomatic Swift patterns, type safety, and modern concurrency for production-ready code.

Quick Start

When to use this skill:

• SwiftUI Development: Building modern declarative UIs for Apple platforms
• Language Features: Using async/await, actors, generics, and modern Swift patterns
• Frameworks: Integrating with Combine, Core Data, CloudKit, StoreKit, URLSession
• Server-Side: Building backend APIs with Vapor, Fluent ORM, Swift NIO
• Migration: Modernizing legacy Objective-C to Swift 6

Core Capabilities

1. SwiftUI Development

Declarative UI framework for all Apple platforms (iOS, macOS, watchOS, tvOS).

Key Areas:

• State Management: @State, @Binding, @StateObject, @EnvironmentObject, @Environment
• Navigation: NavigationStack, NavigationSplitView, TabView, modal presentations
• Views: Lists, Forms, Grids, ScrollView, custom modifiers
• Animations & Transitions: Interactive, spring-based, with async support
• Gestures: Tap, long-press, drag, combined gestures
• Performance: LazyVStack/LazyHStack, @ViewBuilder, EquatableView

Deep Dive: [→ SwiftUI Components Reference](references/swiftui_components.md)

Key Patterns:

• State management for responsive UIs: [→ State Management](references/swiftui_components.md#state-management)
• Navigation in iOS 16+: [→ Navigation Stack](references/swiftui_components.md#navigationstack-ios-16)
• Custom view modifiers: [→ View Modifiers](references/swiftui_components.md#view-modifiers)

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2. Swift Language Features

Modern patterns and idioms for idiomatic, type-safe Swift code.

Core Concepts:

• Concurrency (Swift 5.5+): async/await, actors, structured concurrency, TaskGroups
• [→ Complete Concurrency Guide](references/swift_concurrency.md)
• Protocols: Protocol-oriented programming, extensions, associated types
• [→ Protocol Examples](references/swiftlanguagefeatures.md#protocol-oriented-programming)
• Generics: Type parameters, constraints, conditional conformance
• [→ Generics Deep Dive](references/swiftlanguagefeatures.md#generics-and-associated-types)
• Property Wrappers (Swift 5.1+): Custom attribute behavior, projectedValue
• [→ Property Wrapper Patterns](references/swiftlanguagefeatures.md#property-wrappers)
• Result Builders (Swift 5.4+): DSL creation for view hierarchies
• [→ Result Builder Guide](references/swiftlanguagefeatures.md#result-builders)
• Error Handling: throws, Result, async/await, typed throws (Swift 6)
• [→ Error Patterns](references/swiftlanguagefeatures.md#error-handling-patterns)
• Availability: Platform and version annotations
• [→ Platform Availability](references/swiftlanguagefeatures.md#platform-availability)

Version Timeline:

• Swift 5.5: async/await, actors, structured concurrency
• Swift 5.7: Generics improvements, if let shorthand
• Swift 5.9: Macros, parameter packs, @Observable macro
• Swift 6.0: Complete concurrency checking, typed throws

[→ Full Swift Language Features Reference](references/swiftlanguagefeatures.md)

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3. iOS/macOS Frameworks

Essential Apple platform frameworks for native app development.

Framework Overview:

| Framework | Purpose | Use When | |-----------|---------|----------| | Combine | Reactive programming | Data binding, reactive flows | | Core Data | Local data persistence | Structured data storage, querying | | CloudKit | Cloud sync & sharing | Multi-device sync, collaboration | | StoreKit 2 | In-app purchases | Monetization, subscriptions | | URLSession | Networking | API requests, async/await |

Key Patterns:

• Core Data: @FetchRequest in SwiftUI, background contexts, relationships
• [→ Core Data Setup & Usage](references/iosmacosframeworks.md#core-data)

• CloudKit: Database management, subscriptions, record sharing
• [→ CloudKit Guide](references/iosmacosframeworks.md#cloudkit)

• StoreKit 2: Product loading, purchase flows, transaction handling
• [→ Modern In-App Purchases](references/iosmacosframeworks.md#storekit-2)

• URLSession: Async/await networking, error handling
• [→ Networking Patterns](references/iosmacosframeworks.md#urlsession-and-networking)

• Combine: Publishers, operators, subscribers
• [→ Combine Framework](references/combine_framework.md)

[→ Complete iOS/macOS Frameworks Guide](references/iosmacosframeworks.md)

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4. Server-Side Swift

Backend services with Vapor, Fluent ORM, and Swift NIO.

Frameworks:

• Vapor: Web framework with routing, middleware, async/await
• REST API endpoints, middleware stack, authentication, validation
• [→ Vapor Framework Guide](references/serversideframeworks.md#vapor-framework)

• Fluent ORM: Type-safe database interaction
• Model definitions, relationships, migrations, querying
• [→ Fluent ORM Reference](references/serversideframeworks.md#fluent-orm)

• Swift NIO: Low-level async networking
• Custom protocols, EventLoopFuture, channel handlers
• [→ Swift NIO Guide](references/serversideframeworks.md#swift-nio)

Databases: PostgreSQL, MongoDB, Redis, SQLite Deployment: Docker, Kubernetes, environment configuration

[→ Complete Server-Side Frameworks Guide](references/serversideframeworks.md)

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5. Objective-C Migration

Modernize legacy Objective-C to Swift 6.

Migration Strategy (5 Phases):

1. Assessment - Use scripts/migration_analyzer.py to identify opportunities
2. Foundation - Migrate models and utilities first
3. Swift 6 Modernization - GCD → Task, locks → actors, KVO → @Observable
4. UI Layer - Update views incrementally with MainActor
5. Polish - Enable complete concurrency checking

Key Modernizations:

• Concurrency: From GCD (dispatch_async, queues) to Task-based structured concurrency
• [→ Concurrency Migration](references/objctoswift6_migration.md#concurrency-migration)

• Data Flow: From KVO to @Observable macro, NSNotificationCenter to AsyncStream
• [→ Data Flow Migration](references/objctoswift6_migration.md#data-flow-state)

• Interoperability: Bridging headers, @objc exposure, nullability
• [→ Objective-C Interop](references/objc_interop.md)

[→ Complete Migration Guide](references/objctoswift6migration.md) [→ Bridging & Interop Patterns](references/objcinterop.md)

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Response Guidelines

Initial Assessment Questions

When helping with Swift development, clarify:

1. Target platform(s): iOS, macOS, watchOS, tvOS, server
2. Minimum Swift version: Language features depend on Swift version
3. Deployment target: iOS 15+, macOS 12+, etc.
4. Architecture: SwiftUI vs UIKit/AppKit, MVVM vs other patterns

Code Quality Standards

Follow these principles:

• Swift API Design Guidelines: Naming, parameter labels, clarity
• Access Control: private, fileprivate, internal, public appropriately
• Type Safety: Leverage Swift's type system, avoid force unwrapping
• Error Handling: Use throws, Result, or optionals appropriately
• [→ Error Handling Patterns](references/swiftlanguagefeatures.md#error-handling-patterns)
• Testability: Dependency injection, modular design
• [→ Design Patterns](references/design_patterns.md)

Design Patterns

Proven architectural approaches for maintainable code:

• MVVM: Model-View-ViewModel for SwiftUI apps
• [→ MVVM Pattern](references/design_patterns.md#mvvm-with-swiftui)

• Dependency Injection: Constructor, property, method injection
• [→ DI Patterns](references/design_patterns.md#dependency-injection)

• Repository Pattern: Abstract data access, swap implementations
• [→ Repository Pattern](references/design_patterns.md#repository-pattern)

• Coordinator: Navigation and flow management
• [→ Coordinator Pattern](references/design_patterns.md#coordinator-pattern)

[→ Complete Design Patterns Guide](references/design_patterns.md)

Testing Approach

• Unit Tests: Test business logic with XCTest
• Async Tests: async throws test functions
• Test Doubles: Mocks, stubs, fakes for dependencies
• TDD: Test-driven development workflows

[→ Testing Strategies](references/testing_strategies.md)

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Reference Library

Complete guides organized by category:

Language & Patterns

• [Swift Language Features](references/swiftlanguagefeatures.md) - Protocols, generics, property wrappers, error handling, version management
• [Swift Concurrency](references/swift_concurrency.md) - async/await, actors, TaskGroups, async sequences, structured concurrency
• [Design Patterns](references/design_patterns.md) - MVVM, DI, Repository, Coordinator, composition patterns

Frameworks

• [SwiftUI Components](references/swiftui_components.md) - Views, modifiers, navigation, animations, gestures, state management
• [iOS/macOS Frameworks](references/iosmacosframeworks.md) - Core Data, CloudKit, StoreKit 2, URLSession, framework overview
• [Combine Framework](references/combine_framework.md) - Publishers, operators, subscribers, reactive patterns

Platform-Specific

• [Server-Side Frameworks](references/serversideframeworks.md) - Vapor, Fluent ORM, Swift NIO, WebSockets, authentication
• [Swift Package Manager](references/swiftpackagemanager.md) - Package configuration, dependencies, multi-target projects
• [Testing Strategies](references/testing_strategies.md) - XCTest, mocking, async testing, TDD approaches

Migration & Interop

• [Objective-C to Swift 6 Migration](references/objctoswift6_migration.md) - Comprehensive guide with concurrency, data flow, and pattern translations
• [Objective-C Interop](references/objc_interop.md) - Bridging headers, @objc exposure, nullability, blocks to closures

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Tools & Resources

Scripts

• scripts/migration_analyzer.py - Analyze Objective-C code for Swift 6 opportunities
• Detects legacy concurrency patterns, KVO usage, error handling patterns
• Provides specific migration recommendations

• scripts/swift_package_init.py - Initialize Swift Package Manager projects
• Sets up Package.swift, directory structure, git configuration

Templates

• SwiftUI app - Complete app template with MVVM architecture
• Vapor server - REST API boilerplate with database integration
• Package - Swift Package Manager library template

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Accessing Official Documentation

Use WebFetch to retrieve current Swift documentation:

• Swift Language Guide - Official language reference
• Apple Frameworks - Platform framework documentation
• Vapor Docs - Server-side Swift framework
• Swift Evolution - Language proposals and changes

Use WebFetch when asking about latest API changes, feature availability, or official best practices.

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Development Philosophy: Write idiomatic Swift that leverages type safety, optionals, and protocol-oriented design. Prefer value types (struct, enum) over reference types unless reference semantics are needed. Use modern async/await concurrency, avoid legacy GCD patterns, and apply @MainActor for UI code.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: totallyGreg
• Source: totallyGreg/claude-mp
• License: MIT
• Homepage: https://github.com/totallyGreg/claude-mp

Install and usage instructions live in the source repository linked above.