modern-swift

Name: modern-swift
Author: johnrogers

222stars19forks

How to install modern-swift?

johnrogers/claude-swift-engineering/modern-swift

$npx -y skills add johnrogers/claude-swift-engineering --skill modern-swift

Installs into the current project.

Summary

Use when writing async/await code, enabling strict concurrency, fixing Sendable errors, migrating from completion handlers, managing shared state with actors, or using Task/TaskGroup for concurrency.

Files · 1

View on GitHub

SKILL.md

1	# Modern Swift (6.2+)
2
3	Swift 6.2 introduces strict compile-time concurrency checking with async/await, actors, and Sendable constraints that prevent data races at compile time instead of runtime. This is the foundation of safe concurrent Swift.
4
5	## Overview
6
7	Modern Swift replaces older concurrency patterns (completion handlers, DispatchQueue, locks) with compiler-enforced safety. The core principle: if it compiles with strict concurrency enabled, it cannot have data races.
8
9	## Quick Reference
10
11	\| Need \| Use \| NOT \|
12	\|------\|-----\|-----\|
13	\| Async operation \| `async/await` \| Completion handlers \|
14	\| Main thread work \| `@MainActor` \| `DispatchQueue.main` \|
15	\| Shared mutable state \| `actor` \| Locks, serial queues \|
16	\| Parallel tasks \| `TaskGroup` \| `DispatchGroup` \|
17	\| Thread safety \| `Sendable` \| `@unchecked` everywhere \|
18
19	## Core Workflow
20
21	When writing async Swift code:
22	1. Mark async functions with `async`, call with `await`
23	2. Apply `@MainActor` to view models and UI-updating code
24	3. Use `actor` instead of locks for shared mutable state
25	4. Check `Task.isCancelled` or call `Task.checkCancellation()` in loops
26	5. Enable strict concurrency in Package.swift for compile-time safety
27
28	## Reference Loading Guide
29
30	ALWAYS load reference files if there is even a small chance the content may be required. It's better to have the context than to miss a pattern or make a mistake.
31
32	\| Reference \| Load When \|
33	\|-----------\|-----------\|
34	\| [Concurrency Essentials](references/concurrency-essentials.md) \| Writing async code, converting completion handlers, using `await` \|
35	\| [Swift 6 Concurrency](references/swift6-concurrency.md) \| Using `@concurrent`, `nonisolated(unsafe)`, or actor patterns \|
36	\| [Task Groups](references/task-groups.md) \| Running multiple async operations in parallel \|
37	\| [Task Cancellation](references/task-cancellation.md) \| Implementing long-running or cancellable operations \|
38	\| [Strict Concurrency](references/strict-concurrency.md) \| Enabling Swift 6 strict mode or fixing Sendable errors \|
39	\| [Macros](references/macros.md) \| Using or understanding Swift macros like `@Observable` \|
40	\| [Modern Attributes](references/modern-attributes.md) \| Migrating legacy code or using `@preconcurrency`, `@backDeployed` \|
41	\| [Migration Patterns](references/migration-patterns.md) \| Modernizing delegate patterns or UIKit views \|
42
43	## Common Mistakes
44
45	1. `@unchecked Sendable` as a quick fix — Using `@unchecked Sendable` to silence compiler errors means you've opted out of safety. If the error persists after `@unchecked`, your code has a potential data race. Fix the underlying issue instead.
46
47	2. Missing `await` at call sites — Forgetting `await` when calling async functions is a compiler error, but checking `Task.isCancelled` in a loop without calling `Task.checkCancellation()` silently ignores cancellation.
48
49	3. Capturing `self` in async blocks without `weak` — Holding a strong reference to `self` in a long-running async task prevents deinit. Always use `[weak self]` in closures or use `.task` which auto-manages the lifecycle.
50
51	4. Not checking task cancellation — Long-running operations should regularly check `Task.isCancelled` or call `Task.checkCancellation()`, otherwise cancellation signals are ignored.
52
53	5. Forgetting `@MainActor` on UI code and test suites — Main test struct and view models that update `@Published` properties need `@MainActor`. Forgetting it silently allows cross-thread mutations. Apply `@MainActor` to: view models, view structs, main test structs, and any type that touches UI.
54
55	6. Actor re-entrancy surprises — `await` inside an actor method can release the lock temporarily. Another task may modify actor state. Design actor methods assuming state can change between `await` points.

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6 picks

Type

modern-swift

222stars19forks

View on GitHub

How to install modern-swift?

johnrogers/claude-swift-engineering/modern-swift

$npx -y skills add johnrogers/claude-swift-engineering --skill modern-swift

Installs into the current project.

Summary

Use when writing async/await code, enabling strict concurrency, fixing Sendable errors, migrating from completion handlers, managing shared state with actors, or using Task/TaskGroup for concurrency.

Files · 1

View on GitHub

SKILL.md

1	# Modern Swift (6.2+)
2
3	Swift 6.2 introduces strict compile-time concurrency checking with async/await, actors, and Sendable constraints that prevent data races at compile time instead of runtime. This is the foundation of safe concurrent Swift.
4
5	## Overview
6
7	Modern Swift replaces older concurrency patterns (completion handlers, DispatchQueue, locks) with compiler-enforced safety. The core principle: if it compiles with strict concurrency enabled, it cannot have data races.
8
9	## Quick Reference
10
11	\| Need \| Use \| NOT \|
12	\|------\|-----\|-----\|
13	\| Async operation \| `async/await` \| Completion handlers \|
14	\| Main thread work \| `@MainActor` \| `DispatchQueue.main` \|
15	\| Shared mutable state \| `actor` \| Locks, serial queues \|
16	\| Parallel tasks \| `TaskGroup` \| `DispatchGroup` \|
17	\| Thread safety \| `Sendable` \| `@unchecked` everywhere \|
18
19	## Core Workflow
20
21	When writing async Swift code:
22	1. Mark async functions with `async`, call with `await`
23	2. Apply `@MainActor` to view models and UI-updating code
24	3. Use `actor` instead of locks for shared mutable state
25	4. Check `Task.isCancelled` or call `Task.checkCancellation()` in loops
26	5. Enable strict concurrency in Package.swift for compile-time safety
27
28	## Reference Loading Guide
29
30	ALWAYS load reference files if there is even a small chance the content may be required. It's better to have the context than to miss a pattern or make a mistake.
31
32	\| Reference \| Load When \|
33	\|-----------\|-----------\|
34	\| [Concurrency Essentials](references/concurrency-essentials.md) \| Writing async code, converting completion handlers, using `await` \|
35	\| [Swift 6 Concurrency](references/swift6-concurrency.md) \| Using `@concurrent`, `nonisolated(unsafe)`, or actor patterns \|
36	\| [Task Groups](references/task-groups.md) \| Running multiple async operations in parallel \|
37	\| [Task Cancellation](references/task-cancellation.md) \| Implementing long-running or cancellable operations \|
38	\| [Strict Concurrency](references/strict-concurrency.md) \| Enabling Swift 6 strict mode or fixing Sendable errors \|
39	\| [Macros](references/macros.md) \| Using or understanding Swift macros like `@Observable` \|
40	\| [Modern Attributes](references/modern-attributes.md) \| Migrating legacy code or using `@preconcurrency`, `@backDeployed` \|
41	\| [Migration Patterns](references/migration-patterns.md) \| Modernizing delegate patterns or UIKit views \|
42
43	## Common Mistakes
44
45	1. `@unchecked Sendable` as a quick fix — Using `@unchecked Sendable` to silence compiler errors means you've opted out of safety. If the error persists after `@unchecked`, your code has a potential data race. Fix the underlying issue instead.
46
47	2. Missing `await` at call sites — Forgetting `await` when calling async functions is a compiler error, but checking `Task.isCancelled` in a loop without calling `Task.checkCancellation()` silently ignores cancellation.
48
49	3. Capturing `self` in async blocks without `weak` — Holding a strong reference to `self` in a long-running async task prevents deinit. Always use `[weak self]` in closures or use `.task` which auto-manages the lifecycle.
50
51	4. Not checking task cancellation — Long-running operations should regularly check `Task.isCancelled` or call `Task.checkCancellation()`, otherwise cancellation signals are ignored.
52
53	5. Forgetting `@MainActor` on UI code and test suites — Main test struct and view models that update `@Published` properties need `@MainActor`. Forgetting it silently allows cross-thread mutations. Apply `@MainActor` to: view models, view structs, main test structs, and any type that touches UI.
54
55	6. Actor re-entrancy surprises — `await` inside an actor method can release the lock temporarily. Another task may modify actor state. Design actor methods assuming state can change between `await` points.

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6 picks

Type