Solving the onSnapshot Data Fetching Problem in React Native with Firebase

Discover how to handle data loading with `onSnapshot` in React Native using Redux. Learn strategies to wait for your Firebase data without flickering.
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Solving the onSnapshot Data Fetching Problem in React Native with Firebase

When developing mobile applications using React Native with Expo, integrating Firebase can enhance your app's functionality significantly. However, you might encounter a challenge when trying to fetch data using the onSnapshot method from Firestore. The heart of the issue lies in the fact that onSnapshot does not return a promise, which can complicate the loading states in your app. This guide aims to break down this problem and provide a clear solution to manage your app's data fetching without unnecessary flickering.

The Problem

You're likely trying to subscribe to your Firestore data at the startup of your React Native application. Your current approach fetches data using onSnapshot, but since it does not return a promise, you cannot chain it effectively with your loading component. This leads to a situation where your app could fetch the same data twice when initializing, causing a flicker effect as it briefly loads with incomplete data.

Key Issues:

No Promise Returned: onSnapshot does not provide a promise, making it difficult to control the loading state.

Double Fetching: The need to fetch data both at startup and through the subscription results in multiple calls to Firestore, which is inefficient.

The Solution

To handle this problem effectively, consider adding a "loading" state to your Redux store. This additional state will be used to manage the UI during data fetching. Here’s how you can implement this solution step-by-step.

Step 1: Modify Firebase Subscription with Loading State

You need to incorporate actions in Redux to signify the start and end of a data fetch operation. Updating your useInitFirebaseSubscriptions function will look like this:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Handle Loading State in the Component

Next, in your component where data is rendered, you'll need to check this loading state. If data is still being fetched, you can show a loading indicator, like so:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Managing Different States

It’s also a good idea to manage various states resulting from data fetching, such as empty results or errors. You can add additional conditional rendering within your Manager component based on the fetched data's status.

Additional Considerations

Redux State Management: Make sure your Redux state is well structured to reflect all relevant fetching states.

User Experience: Providing feedback to users during data loading can greatly enhance user experience. Consider adding animations or messages to guide users.

Conclusion

By implementing a loading state through Redux, you can control the user experience during data fetching without the flickering effect caused by double-fetching data from Firebase. This approach not only streamlines your data management but also keeps your UI responsive and engaging. Remember, a clean and pleasant app experience hinges on how well you manage these loading states!