# Swift

> Swift Skill Architecture

- Skill: `j4flmao/swift` (Agent Skill, multi-file: 5 files)
- Install (CLI): `npx skillmds@latest add j4flmao/swift`
- Raw SKILL.md: https://api.skillmd.com/api/skills/j4flmao/swift/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: j4flmao (https://skillmd.com/u/j4flmao)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/j4flmao/swift

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# Swift Skill Architecture

## 1. Skill Context
**Focus**: iOS, macOS, watchOS development, Protocol-Oriented Programming (POP), safe memory management (ARC).
**Triggers**: swift, ios, xcode, protocol-oriented, arc, SwiftUI, UIKit.

## 2. Core Principles
- **Protocol-Oriented Programming (POP)**: Swift prefers protocols and protocol extensions over deep class inheritance. This avoids the fragile base class problem and favors composition.
- **Value Types over Reference Types**: Structs and Enums are value types (allocated on the stack, copied on assignment). Swift heavily encourages using structs for state management to avoid unintended side effects.
- **Automatic Reference Counting (ARC)**: Swift does not have a Garbage Collector. It counts references at compile/runtime. Developers must explicitly manage strong reference cycles using `weak` and `unowned` references.

## 3. Anti-Patterns
- **Force Unwrapping (`!`)**: Crashing the app because an optional is suddenly `nil`. Always use `if let` or `guard let`.
- **Massive View Controller (MVC)**: Putting all network, UI, and business logic inside a `UIViewController`. Use MVVM, VIPER, or TCA (The Composable Architecture) instead.
- **Retain Cycles in Closures**: Forgetting `[weak self]` in an escaping closure (like a network request callback), causing memory leaks because the closure captures the class instance strongly.

## 4. References
- `references/swift-fundamentals.md` — Optionals, Value Types, Closures.
- `references/swift-advanced.md` — Actors, Property Wrappers, Result Builders.
- `references/swift-testing.md` — XCTest and UI Testing.