Скачать или смотреть How to Access sub-sub-collections in Firebase with Flutter

Learn how to effectively update data in `sub-sub-collections` in Firebase Firestore using Flutter, even when you don't have the necessary IDs.
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This video is based on the question https://stackoverflow.com/q/75438431/ asked by the user 'Sara Almashharawi' ( https://stackoverflow.com/u/17551286/ ) and on the answer https://stackoverflow.com/a/75438678/ provided by the user 'Alex Sunder Singh' ( https://stackoverflow.com/u/7997083/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Navigating the Firestore Structure in Flutter

When working with nested collections in Firebase Firestore through Flutter, developers often face challenges, especially when they need to access documents in a sub-sub-collection. In this post, we'll tackle a common issue where you want to update data in a deep collection, but lack the necessary document IDs. We’ll walk through the solution step-by-step.

Problem Overview

In this scenario, our Firestore collection structure looks like this:

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

You might need to update certain data within the drugsTime sub-collection based on the user's actions, but you might not know the specific document IDs for both the drugs and drugsTime collections. This problem can lead to complications and errors in your application, as you've likely encountered an error message that indicates a type mismatch while trying to access Firestore data.

Example Error

The error message reads as follows:

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

This issue arises due to an oversight regarding the use of the await keyword when calling asynchronous methods in Dart.

Solution: Correcting the Asynchronous Call

To properly fetch data from Firestore and update your sub-sub-collection, you need to ensure that all asynchronous calls are awaited. Let's go through the changes needed in your code to resolve the issue.

Step 1: Fetch Document ID from drugs Collection

First, retrieve the document ID from the drugs collection. Your code already achieves this, but let’s ensure clarity:

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

Step 2: Correctly Access the drugsTime Collection

Now, let’s address the code where you retrieve documents from the drugsTime collection. You were missing the await keyword, causing the type mismatch error. Here’s how to correct it:

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

Step 3: Update the Document

Once you've accurately retrieved the documents from the drugsTime sub-collection, you can then proceed to update the required document(s):

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

Conclusion

By following these steps, you can efficiently navigate Firebase Firestore's nested collections and resolve issues related to missing document IDs. Remember to always use await when calling any asynchronous functions to prevent type-related errors. This approach ensures that your code runs smoothly, improving the user experience in your application.

If you encounter further challenges or have questions about using Flutter with Firestore, feel free to reach out for assistance. Happy coding!