noob question about auto-saving onSnapshot

[axzr]

Hi!

mst noob here. I've done some googling around, and I'm still stuck so I'm hoping that you might be able to help me.

atm I have a very naive trigger to save model updates. It looks like this:

    const afterCreate = () => {
      // this ideally shouldn't fire if the model
      // has just been loaded from the database
      self.save();

      onSnapshot(self, self.save);
    };

This mostly works fine, but it does have the odd side effect that when the model is loaded from the database it will immediately save again, which isn't ideal. Is there a way for me to tell the 'source of creation' somehow? Or should I be testing for something different? I thought about adding a flag to the model to say what last caused it to update, but that feels hacky.

Or am I just going about this the wrong way entirely?

[BrianHung]

Move onSnapshot out of afterCreate.

[axzr]

Hi Brian,

Thanks for your reply. As a noob I don't quite follow how this solves my problem. Could you elaborate please?

Cheers!

[antondomratchev]

Hello @axzr,

The reason you have a double save is because it is referenced in both the afterCreate hook as well as onSnapshot reaction. If you are looking to perform the self.save() only when the model is updated, then you only need to call self.save() in onSnapshot reaction. It is ok to have your onSnapshot reaction setup in the afterCreate this will setup the reaction for you every time this model instance is created. Take a look at the Lifecycle documentation for a better understanding when each hook is called. To better understand what you are getting in the onSnapshot reaction take a look here

[axzr]

Hey, thanks for your reply.

I took out the initial save from the afterCreate method. I just had to move the initial save into a different method for those models created by the user. Seems to do the trick!

[coolsoftwaretyler]

Marking @BrianHung's answer as correct here. Thanks all!