How to Fetch Data from User Model Class in Firebase with Flutter

Описание: Discover how to properly retrieve user data in your Flutter app using Firebase, avoid common pitfalls, and enhance your coding efficiency.
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This video is based on the question https://stackoverflow.com/q/67391442/ asked by the user 'Harry' ( https://stackoverflow.com/u/13147529/ ) and on the answer https://stackoverflow.com/a/67391995/ provided by the user 'Tarik Huber' ( https://stackoverflow.com/u/5519300/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving Data Fetching Issue in User Model Class with Firebase and Flutter

Building an application using Firebase and Flutter can be an exciting journey, but it often comes accompanied by a series of challenges, particularly when it comes to fetching and managing user data. In this post, we will explore a specific problem related to retrieving data from a User Model class in a Flutter app and how to solve it efficiently.

The Problem: Data Inaccessibility Error

When attempting to access user data stored in Firestore, many developers encounter errors due to improper asynchronous handling and missing await keywords. In your case, you encountered an error message indicating:

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This error occurs when the fetched data is not properly retrieved or is null, leading to a failed attempt to access fields.

Context: Your Current Structure

You have defined a Users model that retrieves user information from Firestore:

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The challenge lies in the correct implementation of data fetching functions, particularly concerning:

Properly saving user data to Firestore.

Using await to ensure that operations complete before attempting to access the results.

The Solution: Incorporating await for Proper Asynchronous Handling

To fix the errors related to fetching user data, we need to ensure that await is used where necessary to wait for asynchronous operations to complete. Let's break down the critical areas that require this adjustment.

1. Updating the searchController Method

The searchController method should be declared as async, and the call to Firestore should include the await keyword:

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2. Adjusting the User Data Saving Method

In your saveUserInfoToFirestore method, ensure to add await appropriately when saving the user data:

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3. Implementing Safe Data Rendering

Finally, check to ensure that there is valid data before attempting to use it. For instance, adjust the displayUsersFoundScreen method:

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Conclusion

By implementing these changes, you will avoid the null errors and ensure that your app retrieves and displays user data correctly without interruptions. Remember, incorporating the await keyword is essential for effective handling of asynchronous calls within your Flutter applications.

If you continue to run into issues, double-check your Firestore rules and ensure that the document paths you're querying align with what you've defined in your Firestore database. Happy coding!