Automatic Disposal

TL;DR: Always dispose Effects and Observations, the rest will be disposed automatically.

By default when you create a Signal, Computed, Resource or Effect the library will dispose them automatically.

You can customize this behaviour for a specific trackable Object using the options, for example for a Signal you have to create it with autoDispose set to false.

final counter = Signal(0, autoDispose: false);

If you want to disable it globally instead, use

SolidartConfig.autoDispose = false;

The automatic disposal happens automatically when there are no longer subscribers and listeners (for Signal, Computed, Resource) and when the currently tracked dependencies are all disposed (for Effect).

There is a single case that the automatic disposal won't cover:

final count = Signal(0);

@override
void initState() {
  super.initState();
  Effect((_) {
      print("The count is ${count.value}");
    },
  );
}

@override
void dispose() {
  // nothing disposed manually here
  super.dispose();
}

In the example above the count signal will not be disposed because the Effect is a subscriber, and the Effect won't be disposed because the count that watches is not disposed. So they're going to be alive forever. In order to fix this we need to dispose the Effect manually:

final count = Signal(0);
late final DisposeEffect disposeEffect;

@override
void initState() {
  super.initState();
  disposeEffect = Effect((_) {
      print("The count is ${count.value}");
    },
  );
}

@override
void dispose() {
  disposeEffect();
  super.dispose();
}

In this case the count signal would be disposed because the subscriber is disposed and no longer watches it. This would work also if you disposed only the count instead of the Effect.

But I suggest to always dispose the Effect because it's always one, but if it is tracking multiple signals, all of them need to be disposed in order for the effect to dispose, for example:

final count = Signal(0);
final name = Signal('Alex');

@override
void initState() {
  super.initState();
  Effect((_) {
      print("The count is ${count.value} and the name is ${name.value}");
    },
  );
}

@override
void dispose() {
  count.dispose();
  name.dispose();
  super.dispose();
}

As you can see both the count and name signals needs to be disposed in order for the Effect to dispose. This is the reason why I suggest to always dispose the Effect.

In any case, don't worry to call dispose() yourself. It won't produce any error if it's already disposed. It just skips the operation. In fact in the source code the operation is skipped if the object is already disposed:

@override
void dispose() {
  // ignore if already disposed
  if (_disposed) return;
  ...
}