coding-dart

Purpose

This skill provides expertise in Dart 3 programming, focusing on features like null safety, async/await, streams, isolates, Flutter integration, and pub package management, to assist in writing efficient, safe code for apps and tools.

When to Use

Use this skill for Dart 3 projects involving mobile apps (e.g., Flutter), concurrent processing, asynchronous operations, or package dependencies. Apply it when null safety is critical to avoid runtime errors, or for handling real-time data with streams.

Key Capabilities

• Null Safety: Enforce non-nullable types using late for lazy initialization and required for parameters, e.g., late String name; to declare a variable that must be initialized before use.

• Async/Await: Handle asynchronous code with Future and async functions, such as Future<void> fetchData() async { var data = await http.get('/api/data'); } .

• Streams: Manage asynchronous data streams using Stream from dart:async , e.g., Stream<int> countStream() async* { for (int i = 0; i < 5; i++) yield i; } .

• Isolates: Run concurrent tasks with Isolate for CPU-bound operations, e.g., Isolate.spawn(workerFunction, args); to offload work.

• Flutter Integration: Build UI with widgets and state management, e.g., using StatelessWidget for simple components.

• Pub Package Manager: Manage dependencies via pub, including adding packages with pub add package_name .

Usage Patterns

To accomplish tasks, structure code with null safety by always specifying types (e.g., String? optionalString; for nullable values). For async operations, wrap I/O in async functions and use await for readability. Use isolates for background tasks to avoid UI blocking. Integrate Flutter by starting with MaterialApp in main.dart . For package management, run pub get after editing pubspec.yaml . Always test with dart test before deployment.

Common Commands/API

• Dart CLI Commands: Use dart analyze with flags like --fatal-infos to enforce strict checks; run scripts with dart run bin/main.dart . For async, import dart:async and use Future.delayed(Duration(seconds: 1), () => print('Delayed')); .

• Pub Commands: Add dependencies with pub add http --major-version 1 for specific versions; update with pub upgrade ; build packages with pub build --release .

• Key APIs: Access streams via StreamController for custom streams, e.g., var controller = StreamController<int>(); controller.add(1); . For isolates, use Isolate.run for simple tasks: Isolate.run(() => computeHeavyTask()); .

• Config Formats: Edit pubspec.yaml for dependencies, e.g.: dependencies: http: ^1.0.0

Use environment variables for secrets, e.g., set $API_KEY and access via String.fromEnvironment('API_KEY') .

Integration Notes

Integrate Dart with Flutter by adding Flutter dependencies in pubspec.yaml and running flutter pub get . For external APIs, set environment variables like $FLUTTER_API_KEY and access in code via Platform.environment['FLUTTER_API_KEY'] . Combine with other tools by using Dart's FFI for C libraries or integrating with VS Code via the Dart extension (install with code --install-extension Dart-Code.dart-code ). Ensure Dart SDK is in PATH; verify with dart --version .

Error Handling

Handle errors in async code with try-catch in async functions, e.g.:

try { var result = await fetchData(); } catch (e) { print('Error: $e'); }

For streams, use onError callbacks: stream.listen((data) => print(data), onError: (error) => print(error)) . Check null safety errors with dart analyze , and use rethrow to propagate exceptions. For isolates, handle communication errors with ReceivePort and SendPort .

Concrete Usage Examples

• Async HTTP Request: To fetch data safely with null safety, use: import 'package:http/http.dart' as http; Future<String?> getData() async { try { var response = await http.get(Uri.parse('https://api.example.com/data')); return response.body; } catch (e) { return null; } } Then call it with var data = await getData(); if (data != null) print(data); .

• Flutter Widget with Stream: Create a simple counter stream in Flutter: import 'dart:async'; class MyWidget extends StatelessWidget { Stream<int> counter() async* { for (int i = 0; i < 5; i++) yield i; } @override Widget build(BuildContext context) { return StreamBuilder<int>( stream: counter(), builder: (context, snapshot) => Text(snapshot.data?.toString() ?? '0'), ); } } .

Graph Relationships

• Related to cluster: coding (e.g., shares tags with coding-flutter for Flutter-specific tasks).

• Connected via tags: dart (links to general programming skills), flutter (integrates with UI-focused skills), coding (groups with other language skills like coding-python).