What is Destroyer in dart ?

Overview

Dart does not have a traditional "destructor" like C++ (

~ClassName()

dispose()

Dart Memory Management

Dart uses an automatic garbage collector — memory is freed when objects are no longer referenced. You don't manually destroy objects.

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void main() {
  var obj = HeavyObject(); // Created in heap
  obj.doSomething();
  // When obj goes out of scope or is reassigned,
  // GC eventually frees the memory — no destructor needed
  obj = null; // ← hints it can be collected (if nullable)
}

The Finalizer Class (Dart 2.17+)

Dart 2.17 introduced

Finalizer

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final finalizer = Finalizer<String>((message) {
  print('Object collected: $message');
});

class Resource {
  Resource() {
    finalizer.attach(this, 'Resource cleanup', detach: this);
  }

  void close() {
    finalizer.detach(this);
    // Manual cleanup
  }
}

⚠️

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Finalizer

is not deterministic — you don't know exactly when it runs. Prefer explicit

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dispose()

.

dispose() — Flutter's Lifecycle Teardown

In Flutter, the closest equivalent to a destructor is

dispose()

State

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class MyScreen extends StatefulWidget {
  @override
  _MyScreenState createState() => _MyScreenState();
}

class _MyScreenState extends State<MyScreen> with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  late StreamSubscription _subscription;
  late TextEditingController _textController;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(vsync: this, duration: Duration(seconds: 1));
    _subscription = dataStream.listen((data) => setState(() {}));
    _textController = TextEditingController();
  }

  @override
  void dispose() {
    // 'Destructor' — called when widget is removed from tree
    _controller.dispose();
    _subscription.cancel();
    _textController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) => Container();
}

Other Dispose Patterns

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// ChangeNotifier
class MyNotifier extends ChangeNotifier {
  Timer? _timer;

  void startTimer() { _timer = Timer.periodic(Duration(seconds: 1), (_) {}); }

  @override
  void dispose() {
    _timer?.cancel(); // Clean up timer
    super.dispose();
  }
}

// GetX Controller
class MyController extends GetxController {
  @override
  void onClose() {
    // Destructor equivalent in GetX
    super.onClose();
  }
}

Summary

~ClassName()

dispose()

onClose()

Finalizer

Best Practice: Always override

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dispose()

in

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StatefulWidget

State classes to clean up

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AnimationController

,

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TextEditingController

,

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StreamSubscription

,

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Timer

, and

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FocusNode

objects to prevent memory leaks.