Skill: Dart for Flutter

Purpose

This hub routes Dart-language topics that strongly impact Flutter apps: async correctness, null safety, immutability, extensions, isolates, and error modeling.

When to use

• •You see async lifecycle bugs ("setState after dispose", stale responses, retries).
• •You need safer APIs (null safety, typed errors) or predictable data structures.
• •You want to move CPU work off the UI thread.

When NOT to use

• •Your issue is a layout or rendering problem; start at flutter_core/SKILL.md.
• •Your issue is state management architecture; start at state/SKILL.md.

Core concepts

• •Event loop: Futures and microtasks determine ordering.
• •Null safety: types are contracts; prefer modeling over !.
• •Immutability: predictable state transitions and cheaper tests.
• •Isolates: concurrency by message passing, not shared memory.

Recommended patterns

• •Model failures as data (sealed failures) where UX/testing benefits.
• •Prefer immutable models and copy-on-write updates.
• •Cancel or ignore stale async work when the owner is disposed.
• •Offload CPU-heavy work (JSON decode, sorting large lists) to an isolate.

Minimal example

How to pick a topic:

- Async ordering/cancellation -> async.md
- Null crashes / optional fields -> null_safety.md
- Defensive list/map updates -> collections.md
- Reusable helpers -> extensions.md
- CPU work off UI thread -> isolates.md
- Typed failures -> error_handling.md

Edge cases

• •Async work may complete after navigation; you must check ownership.
• •JSON fields are often missing/nullable; model them explicitly.

Common mistakes

• •Using dynamic to "get it working" and losing type safety.
• •Treating all failures as exceptions instead of modeling expected errors.

Testing strategy

• •Unit test pure Dart logic and error modeling.
• •Use fake clocks/clients to make async tests deterministic.

Related skills

• •Flutter lifecycle
• •Async state modeling
• •Error modeling