Скачать или смотреть Resolving the TypeError: entities is not iterable in NX with NGRX

Discover how to troubleshoot and fix the `TypeError: entities is not iterable` error in your NX and NGRX Angular application. Follow our step-by-step guide to get your project running smoothly.
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Understanding the TypeError: entities is not iterable in NX with NGRX

As developers, we sometimes encounter baffling errors that can halt progress in our projects. One such issue is the TypeError: entities is not iterable when working with NGRX in an NX workspace in Angular. This error can be particularly frustrating, especially if you're a novice using the Entity module for the first time. In this post, we'll explore the causes of this error and how to easily resolve it.

The Problem: Why Are We Seeing This Error?

When you attempt to utilize the Entity module in your NGRX store but get hit with the aforementioned TypeError, it's generally a sign that the data structure you're working with doesn't conform to the expected format. In this case, it means your application's state is not configured properly to iterate over the stored entities when fetching them.

Example Scenario

Consider that you're fetching data from a service that is structured differently than what the Entity module expects. This often happens when you're following a variety of guides that might not be aligned in terms of data structure or Angular version. Let's take a look at a scenario that led to the error, as shared by a developer using Angular9+ .

The Solution: Fixing Our Data Structure

After some confusion and from valuable community feedback, it turns out the solution was rather simple. Here’s the process for correcting the issue:

Step 1: Modify the Service Mock Data

In the highlighted developer's case, the mock data initially returned by the service was structured incorrectly. It was necessary to change this data to ensure it was a standard array of items instead of an excessively nested object structure.

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Step 2: Adjust the Success Action Payload

Once the service data was structured as intended, it was important to ensure that the success action correctly reflected the modified structure. Updating it ensures that you're passing the correct type of data to the action handler:

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Step 3: Recheck Your Reducer and Component Integrations

Lastly, after modifying the data and actions, it’s wise to inspect your reducer and component integrations. Always ensure that they are correctly interacting with the observable streams created by your actions and selectors.

Selector Usage: Ensure you are selecting your data correctly in your component.

NgOnInit: Make sure to dispatch actions to trigger the data fetching process.

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Conclusion

In summary, fixing the TypeError: entities is not iterable in your NX and NGRX application is often about ensuring your data structures align with what NGRX expects. By simplifying the service mock data, appropriately updating your success action, and verifying your interactions in the component, the issue can be resolved promptly. Happy coding, and remember that sometimes the simplest changes can lead to a smooth-running application!