Dart Guide

Applies to: Dart 3.0+, Sound Null Safety, Flutter, Server-side Dart

Core Principles

1. Sound Null Safety: The type system guarantees non-nullable by default; nullable types are explicit
2. Async by Design: Use Futures, Streams, and async/await for all I/O and event-driven logic
3. Immutability First: Prefer final locals, const constructors, and immutable data structures
4. Composition Over Inheritance: Use mixins, extension methods, and sealed class hierarchies
5. Effective Dart: Follow official Effective Dart style for naming, documentation, and API design

Guardrails

Version & Dependencies

• Use Dart 3.0+ with sound null safety enabled (no // @dart=2.x opt-outs)
• Manage dependencies with pubspec.yaml; run dart pub get after changes
• Pin dependency versions with caret syntax (^1.2.0) for libraries, exact for apps