Resolving Angular & NgRx-Data Subscription Issues Like a Pro

Learn how to effectively handle `NgRx-Data` update and subscription issues in your Angular application, ensuring real-time data reflection on your UI.
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This video is based on the question https://stackoverflow.com/q/67063834/ asked by the user 'John McArthur' ( https://stackoverflow.com/u/183425/ ) and on the answer https://stackoverflow.com/a/67072399/ provided by the user 'Fiber' ( https://stackoverflow.com/u/7379044/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Angular & NgRx-Data Subscription Issues

If you've been working with Angular and NgRx-Data, you might have encountered frustrating moments where data on your display page does not update after making changes through an edit modal. This can lead to a confusing experience, especially for users expecting real-time updates. In this blog, we'll explore the common pitfalls in handling data subscriptions and how to effectively update and reflect changes on your UI.

The Problem: Missing Updates After Editing

In a typical Angular application using NgRx-Data, when you update an item (like a site in our case) and close the modal, you might expect the underlying display to immediately reflect that change. However, many developers find that even though they can verify the data in the store or database is updated, the corresponding component displaying that data does not re-render or refresh.

Here’s a brief breakdown of how this scenario presents itself:

Selecting an Item: The user is on a list view and selects an item (site) to view details.

Routing to a Detail Page: The item id is passed, and the detail page subscribes to data updates via getByKey().

Editing in a Modal: When an 'edit' button is clicked, a modal opens with a form for changes.

Submitting an Update: After submitting the form, the item updates successfully, but the display remains unchanged.

Why This Happens

The root of the problem lies in the way data is tied to subscriptions. Simply subscribing to an observable that fetches data from the backend (getByKey) will only return the data once, and it won't automatically trigger the same subscription when the underlying data (store) updates. This means after editing an item, your component does not refresh with the latest state stored in the NgRx store.

The Solution: Subscribing to Store Changes

To fix this issue, we need to establish a connection between your component and the NgRx store directly, using observables. This way, you can listen for changes continuously and update the display when necessary. Here's how to do it step-by-step:

Step 1: Creating a Direct Observable

Use the EntitySelectorsFactory from ngrx/data to create a direct observable that listens to changes in your store. Here’s how you can set it up:

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

Step 2: Understanding the Code

Store Selection: Here, we're selecting the entities from the store which represent our sites. The observable sites$ fires every time there's an update in the store.

Filtering Logic: Using the map function, we filter the results to find the specific site by its ID.

Subscription Management: We wrap our subscriptions in a Subscription object and ensure to clean up in ngOnDestroy to prevent memory leaks.

Conclusion

By tapping directly into the NgRx store using observables, you can ensure your Angular components react to state changes properly, providing a smooth and real-time experience for users. If you've encountered similar issues in your Angular applications, using this approach will greatly enhance your application's responsiveness and user experience.

Bonus Tip

Make sure to handle unsubscription properly to avoid memory leaks, especially when components are destroyed.

By implementing these strategies, you'll be well on your way to mastering data handling with Angular and NgRx-Data.

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