Caching computeds: is it really a thing?

[OnkelTem]

Hey folks, it seems like I'm missing some basic concepts.

Imagine we have a computed:

// in some (auto-)observable class

get fooTitle() {
  return this.t('Foo')
}

And let's put that this.t() is an expensive operation.

It is my understanding, that whenever we call fooTitle getter, it will be re-evaluated and it will invoke this.t(). Isn't that so?

Then what is the true meaning of the following sentence in the docs:

They evaluate lazily, caching their output and only recomputing if one of the underlying observables has changed.

https://mobx.js.org/computeds.html

[mweststrate]

It will only re-evaluate if an observable used by t has changed in the mean time

…

On Wed, May 14, 2025, 13:47 Artiom Neganov ***@***.***> wrote: Hey folks, it seems like I'm missing some basic concepts. Imagine we have a computed: // in some observable class get fooTitle() { return this.t('Foo')} And let's put that this.t() is an expensive operation. It is my understanding, that whenever we call fooTitle getter, it will be re-evaluated and it will trigger this.t() call. Then what does means the following sentence in the docs: They evaluate lazily, caching their output and only recomputing if one of the underlying observables has changed. https://mobx.js.org/computeds.html — Reply to this email directly, view it on GitHub <#4551>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN4NBG7VLY4OVHK6FSG7RT26MUOPAVCNFSM6AAAAAB5DEMCHGVHI2DSMVQWIX3LMV43ERDJONRXK43TNFXW4OZYGMZDGOJQGY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>