Swift Concurrency

Swift 6 strict concurrency patterns – async/await, MainActor, Sendable, actor isolation, and data race prevention.

When to use: Debugging Swift 6 concurrency errors (actor isolation, data races, Sendable warnings), implementing @MainActor classes, converting delegate callbacks to async-safe patterns

Key Features

• Quick decision tree for concurrency errors
• Copy-paste templates for common patterns
  • Delegate capture (weak self)
  • Sendable conformance
  • MainActor isolation
  • Background task patterns
• Anti-patterns to avoid
• Code review checklist

Philosophy: Swift 6's strict concurrency catches bugs at compile time instead of runtime crashes.

TDD Tested: Critical checklist contradiction found and fixed during pressure testing

Example Prompts

These are real questions developers ask that this skill answers:

• "I'm getting 'Main actor-isolated property accessed from nonisolated context' errors everywhere." → Covers Pattern 2 (Value Capture Before Task) that solves most delegate method concurrency errors

• "My code is throwing 'Type does not conform to Sendable' warnings when I try to pass data between background work and MainActor." → Explains Sendable conformance and shows patterns for enums, structs, and classes crossing actor boundaries

• "I have a task stored as a property and it's causing memory leaks. How do I write it correctly with weak self?" → Demonstrates Pattern 3 with the difference between stored and short-lived tasks

• "I'm new to Swift 6 concurrency. What are the critical patterns I need to know?" → Provides 6 copy-paste-ready patterns covering delegates, Sendable, tasks, snapshots, MainActor, and background work

• "How do I know when to use @MainActor vs nonisolated vs @concurrent?" → Clarifies isolation rules with decision tree for each scenario and real-world examples