Swift Concurrency
Diagnose Swift Concurrency issues, refactor callback-based code to async/await, and...
Install
npx skills add AvdLee/Swift-Concurrency-Agent-Skill --skill swift-concurrency -g -a claude-code -y- Repository
- AvdLee/Swift-Concurrency-Agent-Skill1.7k
- Category
- Mobile
- Updated
- 2mo ago
- License
- MIT
- Context cost
- Mediumabout 3,000 tokens
- Runs scripts
- No, instructions only
What it does
Diagnose Swift Concurrency issues, refactor callback-based code to async/await, and guide Swift 6 migration when working with tasks, actors, @MainActor, Sendable, data races, thread safety, or concurrency-related compiler and linter warnings.
Swift Concurrency
Fast Path
Before proposing a fix:
- Analyze
Package.swiftor.pbxprojto determine Swift language mode, strict concurrency level, default isolation, and upcoming features. Do this always, not only for migration work. - Capture the exact diagnostic and offending symbol.
- Determine the isolation boundary:
@MainActor, custom actor, actor instance isolation, ornonisolated. - Confirm whether the code is UI-bound or intended to run off the main actor. When spawning unstructured tasks, inspect the synchronous prefix (everything before the first
await): start on@MainActoronly when that prefix truly needs main-actor access; otherwise useTask { @concurrent in ... }and hop back withMainActor.runonly after the suspension. A trivial non-main line (for example,print) followed by main-actor work in the same prefix is not a reason to use@concurrent. For delayed retries, timers, and backoff tasks, separate the waiting from the UI mutation. The sleep often belongs off the main actor even when the final state update belongs on it.
Project settings that change concurrency behavior:
| Setting | SwiftPM (Package.swift) | Xcode (.pbxproj) |
|---|---|---|
| Language mode | swiftLanguageVersions or -swift-version (// swift-tools-version: is not a reliable proxy) | Swift Language Version |
| Strict concurrency | .enableExperimentalFeature("StrictConcurrency=targeted") | SWIFT_STRICT_CONCURRENCY |
| Default isolation | .defaultIsolation(MainActor.self) | SWIFT_DEFAULT_ACTOR_ISOLATION |
| Upcoming features | .enableUpcomingFeature("NonisolatedNonsendingByDefault") | SWIFT_UPCOMING_FEATURE_* |
| Approachable Concurrency | N/A (use individual upcoming features) | SWIFT_APPROACHABLE_CONCURRENCY |
