onStateChange called after screen's mount (useEffect)

[simonadenic]

onStateChange called after screen's mount (useEffect)

[github-actions]

Hey @simonadenic! Thanks for opening the issue. It seems that the issue doesn't contain a link to a repro.

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[github-actions]

The versions mentioned in the issue for the following packages differ from the latest versions on npm:

• @react-navigation/native (found: 6.0.2, latest: 6.1.17)
• @react-navigation/bottom-tabs (found: 6.0.5, latest: 6.5.20)
• @react-navigation/stack (found: 6.0.7, latest: 6.3.29)

Can you verify that the issue still exists after upgrading to the latest versions of these packages?

[simonadenic]

Here's a reproduction on the snack: https://snack.expo.dev/@simonadenic/getting-started-%7C-react-navigation?platform=android&name=Getting%20started%20%7C%20React%20Navigation&dependencies=%40expo%2Fvector-icons%40

[satya164]

It's working as designed. In many cases such as conditional rendering, it's impossible to know if the state changes until after the components finish re-rendering.

It also seems very unlikely that a button press will happen before useEffect is called. But if you really need to know before screen mounts then you can use events such as __unsafe_action__, however it'll not cover all scenarios.

[github-actions]

Hey! This issue is closed and isn't watched by the core team. You are welcome to discuss the issue with others in this thread, but if you think this issue is still valid and needs to be tracked, please open a new issue with a repro.

[simonadenic]

Hey @satya164, thank you for the answer.

Is there any other way you'd suggest to track analytics, since maybe the suggested way in the docs does not cover all the use cases and doesn't track screen views properly.
Consider the following use case. For the screen view event you're logging, you want to describe it with some data from that particular screen. In the example, I gave, when the user opens SEARCH page, you'd want to know which params he sees on the SEARCH page. You can only do this in the useEffect of the SEARCH page (params could be coming from deep link, push notification, prefilled from some user context etc). So, for example:

<NavigationContainer onStateChange={()=>{
    // conditions 
     logScreenView(); 
}}>

// here we instantiate screens in a navigator
</NavigationContainer>

const SearchScreen = ()=>{
   const params = getParamsSomehow();
   React.useEffect(()=>{
      logSearchEvent({ params }); 
   },[params]);

return <SomeUi/>
}

In the analytics, you'll see that the Search event you logged is connected to the wrong page (since screen view is going to be logged after the search event).

So anytime you want to log some event from any effect in the component, the analytics will show wrong data for these events, as they will not be tied to the correct screen.