Mobx: Do reactions automatically get cleaned up when an observable is not longer present?

[ManuSevenval]

I have a...

• [x] Question
• [x] Did you check this issue wasn't filed before?

Hi!

I am wondering if mobx / GC automatically dispose reactions and observers on observables, that have been dereferenced, or if I have to make sure that their dispose methods get called and thereby release unused memory by myself.

I tried to illustrate the case with the following example:
https://codesandbox.io/s/94zmr52l9w

How could I check, if the reaction is still registered within mobx's tracking cycle?

Thanks!

[mweststrate]

Reactions returns a disposer function that can be used to stop the
observation and thus enable GC. Otherwise, the engine can only GC a
reaction if all things on which the reaction depends can be GC-ed as
well. Something I wouldn't rely on too much :)

Op vr 29 jun. 2018 om 13:15 schreef ManuSevenval [e-mail]:

I have a...

• Question
• Did you check this issue wasn't filed before?

Hi!

I am wondering if mobx / GC automatically dispose reactions and observers
on observables, that have been dereferenced, or if I have to make sure that
their dispose methods get called and thereby release unused memory by
myself.

I tried to illustrate the case with the following example:
https://codesandbox.io/s/94zmr52l9w

How could I check, if the reaction is still registered within mobx's
tracking cycle?

Thanks!

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[ManuSevenval]

thanks for the quick response!
just out of curiosity:

Otherwise, the engine can only GC a
reaction if all things on which the reaction depends can be GC-ed as
well.

in my particular example the reaction looks like this:

reaction(
      () => this.isHungry,
      () => document.getElementById('root').innerHTML = "FEED WALTER!!",
    )

would the GC keep the reaction alive because #root is still present? Or would it be clever enough to notice, that the class instance was killed and collect the reaction anyways?

[mweststrate]

it will be alive as long as this.isHungry is alive. In this case it is
easy to oversee the impact, bug in general I recommend to be a good citizen
and clean up any subscriptions you make. Like you would do in Rx for example

Op vr 29 jun. 2018 om 16:40 schreef ManuSevenval [e-mail]:

thanks for the quick response!
just out of curiosity:

Otherwise, the engine can only GC a

reaction if all things on which the reaction depends can be GC-ed as
well.

in my particular example the reaction looks like this:

reaction(
() => this.isHungry,
() => document.getElementById('root').innerHTML = "FEED WALTER!!",
)

would the GC keep the reaction alive because #root is still present? Or
would it be clever enough to notice, that the class instance was killed and
collect the reaction anyways?

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[ManuSevenval]

alright, thanks! :+1: :+1: