CtrlK
BlogDocsLog inGet started
Tessl Logo

dpearson2699/swift-ios-skills

Agent skills for iOS, iPadOS, Swift, SwiftUI, and modern Apple framework development.

71

Quality

89%

Does it follow best practices?

Impact

—

No eval scenarios have been run

SecuritybySnyk

Advisory

Suggest reviewing before use

Overview
Quality
Evals
Security
Files

diagnostics.mdskills/swift-concurrency/references/

Concurrency Diagnostics

Common Swift concurrency compiler warnings and errors with their fixes.

Diagnostic → Fix Reference

DiagnosticCauseFix
Sending 'x' risks causing data racesPassing a non-Sendable value across isolation boundariesMake the type Sendable, use sending parameter, or restructure to avoid the crossing
Capture of 'x' with non-sendable type in a @Sendable closureClosure captures non-Sendable valueMake type Sendable, copy the value, or use an actor
Non-sendable type 'X' returned by implicitly asynchronous callReturning non-Sendable from cross-isolation callMake return type Sendable or keep work on same isolation
Main actor-isolated property 'x' can not be mutated from a nonisolated contextAccessing @MainActor state from non-main contextAdd @MainActor to caller, use await MainActor.run { }, or restructure
Call to main actor-isolated function in a synchronous nonisolated contextCalling @MainActor function without awaitAdd await, annotate caller @MainActor, or use .task { } in SwiftUI
Actor-isolated property 'x' can not be referenced from a nonisolated contextAccessing actor state without awaitAdd await or move code into the actor
Type 'X' does not conform to protocol 'Sendable'Stored properties aren't all SendableMake properties Sendable, use @unchecked Sendable with a lock, or redesign
Passing closure as a 'sending' parameter risks causing data racesClosure captures values that could raceEnsure captures are Sendable or don't escape the isolation domain
Task-isolated value of type 'X' passed as a strongly transferred parameterMoving a value out of a task unsafelyCopy the value or use sending return
Global variable 'x' is not concurrency-safeMutable global without isolationAdd @MainActor, make it nonisolated(unsafe) (with justification), or use actor

Swift 6.2 Approachable Concurrency Changes

With UpcomingFeature.InferSendableFromCaptures (Swift 6.2):

  • Closures infer Sendable from their captures (fewer explicit annotations needed)
  • nonisolated(nonsending) is the new default for async functions (SE-0461)
  • @concurrent marks functions that intentionally run off-actor

Strict Concurrency Adoption Strategy

  1. Start with StrictConcurrency: targeted in build settings — warns on Sendable issues without full enforcement
  2. Fix warnings bottom-up — start with leaf types (models, DTOs), then services, then UI
  3. Move to StrictConcurrency: complete once warnings are resolved
  4. Use @preconcurrency import temporarily for third-party modules that haven't adopted Sendable — document removal plan

Runtime Diagnostics

Enable the Thread Sanitizer (-sanitize=thread) to catch data races at runtime that the compiler can't statically prove.

Xcode: Edit Scheme → Run → Diagnostics → Thread Sanitizer.

Common TSan findings in concurrent code:

  • Simultaneous reads and writes to Dictionary or Array without actor protection
  • Delegate callbacks arriving on unexpected queues
  • Completion handlers racing with synchronous property access

skills

swift-concurrency

references

approachable-concurrency.md

async-algorithms.md

bridging-interop.md

concurrency-patterns.md

diagnostics.md

swiftui-concurrency.md

synchronization-primitives.md

SKILL.md

CHANGELOG.md

README.md

tile.json