dart-resource-management

name	dart-resource-management
description	Resource lifecycle and disposal for Dart/Flutter. Use when managing Timer, StreamController, subscriptions, animations, network cancellation, file/DB handles, native resources, or preventing memory leaks.

Dart Resource Management

Disposal Pattern

All resources must be cleaned up in dispose() (widgets) or close() (services/repositories). After cancelling or closing any resource, nullify the variable.

_subscription?.cancel();
_subscription = null;

_timer?.cancel();
_timer = null;

_streamController.close();

_animationController.dispose();

Timer

• Use Timer instead of Future.delayed -- Future.delayed cannot be cancelled.
• Timer must be nullable.
• Cancel existing timer before creating a new instance (avoid duplicates).
• Cancel in dispose(); nullify after cancel.

Subscriptions

• Cancel in dispose(); nullify after cancel.
• Example: _subscription?.cancel(); _subscription = null;

StreamController

• Call controller.close() when the controller's owner is disposed or closed.
• Close in: StatefulWidget.dispose(), service/repository close() methods, or when the stream's lifetime scope ends.

Animations and Tickers

• Call controller.dispose() in dispose(); never leave them running after widget removal.

Network

• Cancel in-flight HTTP requests and WebSocket connections on widget disposal.
• Use CancelToken (dio) or equivalent.

Pending Futures

• Check mounted before setState or context usage after async gaps.
• Avoid completing work for disposed widgets.

Files and Database

• Close IOSink, RandomAccessFile, and other file streams; use try-finally for cleanup on error paths.
• Close database connections when no longer needed; don't hold connections across lifecycle boundaries.

Native Resources

• Release cameras, sensors, etc. when no longer needed.
• Call platform-specific release/dispose methods.
• Don't hold native resources across widget disposal or app backgrounding.

Scoping

• Scope resources to the widget or object that owns them.
• Don't store widget-scoped resources in global or long-lived objects.

App Lifecycle

• Use WidgetsBindingObserver for app-level lifecycle.
• pause -- release heavy resources (cameras, large caches) when app goes to background.
• resume -- reacquire if needed.

Memory

• Ensure disposed objects are not retained by closures or references.
• Set image cache eviction policies; don't hold unlimited image data.
• Profile with DevTools to identify leaks.