swift▌

Philosophy: Non-opinionated, correctness-focused. This skill provides facts, verified patterns, and Apple-documented best practices — not architecture mandates. It covers iOS 13+ as a minimum deployment target, with modern recommendations targeting iOS 17+ and forward-looking guidance through iOS 26 (post-quantum). Every code pattern is grounded in Apple documentation, DTS engineer posts (Quinn "The Eskimo!"), WWDC sessions, and OWASP MASTG — never from memory alone.

Use this skill to pick the best Swift architecture playbook for SwiftUI/UIKit codebases and apply it to the user’s task.

Encode and decode Swift types using Codable (Encodable & Decodable) with JSONEncoder, JSONDecoder, and related APIs. Targets Swift 6.3 / iOS 26+.

Swift Concurrency review and remediation for Swift 6.2+ codebases. \n \n Diagnoses and fixes actor isolation, Sendable safety, and data-race warnings through targeted edits that preserve existing behavior \n Applies minimal, concrete fixes: @MainActor annotations, actor isolation, Sendable conformance, and completion-handler-to-async/await migrations \n Triages compiler diagnostics by checking project concurrency settings, actor context, and whether code is UI-bound or background work \n Verifie

Write, review, and improve Swift Testing code with modern APIs and best practices. \n \n Validates test structure, assertions, dependency injection, async patterns, and actor isolation against Swift Testing conventions \n Guides migration from XCTest to Swift Testing, including assertion mappings and modern concurrency patterns \n Covers new features like raw identifiers, test scopes, exit tests, attachments, and range-based confirmations \n Targets Swift 6.2+ with emphasis on modern Swift concu

Write, review, and migrate Swift tests using modern Swift Testing APIs with parallel execution and clear diagnostics. \n \n Covers test structure, #expect / #require macros, traits, tags, parameterized tests, and async waiting patterns for readable, maintainable tests \n Guides incremental XCTest migration while preserving UI automation and performance-metric tests that require XCTest \n Prioritizes parallel-safe test design; recommends fixing shared state before applying .serialized isolation \

Core Principle: Optimize Swift code by understanding language-level performance characteristics—value semantics, ARC behavior, generic specialization, and memory layout—to write fast, efficient code without premature micro-optimization.

Swift Testing is Apple's modern testing framework introduced at WWDC 2024. It uses Swift macros (@Test, #expect) instead of naming conventions, runs tests in parallel by default, and integrates seamlessly with Swift concurrency.

Core Swift language features and modern syntax patterns targeting Swift 6.3. Covers language constructs, type system features, Codable, string and collection APIs, formatting, C interop (@c), module disambiguation (ModuleName::symbol), and performance attributes (@specialized, @inline(always)). For concurrency (actors, async/await, Sendable), see the swift-concurrency skill. For SwiftUI views and state management, see swiftui-patterns.

Modern Swift testing framework with @Test macros, parameterized tests, traits, and async support. \n \n Write unit tests using @Test macros with #expect and #require assertions; prefer Swift Testing over XCTest for all new tests (Xcode 16+, Swift 6+) \n Organize tests with @Suite for grouping, custom tags for filtering, and traits for conditional execution, time limits, and known issues \n Support parameterized tests via arguments: with enum cases, ranges, or cartesian products; use confirmation