---
title: "Swift Patterns"
description: "> This file extends [common/patterns.md](../common/patterns.md) with Swift specific content."
type: skill
canonical_url: https://claudary.paisolsolutions.com/skills/patterns-99
source: "Claudary"
difficulty: intermediate
author: "Claude Code Knowledge Pack"
date: 2026-07-10T11:31:51.869Z
license: CC-BY-4.0
attribution: "Swift Patterns — Claudary (https://claudary.paisolsolutions.com/skills/patterns-99)"
---

# Swift Patterns
> This file extends [common/patterns.md](../common/patterns.md) with Swift specific content.

## Overview

---
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.

---

Source: [Claudary](https://claudary.paisolsolutions.com/skills/patterns-99) · https://claudary.paisolsolutions.com