Resolving the TypeError: Cannot read property 'pipe' of undefined in Angular 14 with NGRX

Learn how to fix the TypeError in your Angular 14 application when using NGRX effects by correctly implementing your service methods to return observables.
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How to Fix the TypeError: Cannot read property 'pipe' of undefined in Angular 14 with NGRX

If you are working with Angular and NGRX, you might have encountered this frustrating error message: TypeError: Cannot read property 'pipe' of undefined. This issue typically arises when there is a problem in the way observables are handled in your effects. In this guide, we will explore how to diagnose and solve this problem effectively.

Understanding the Issue

The error occurs in the context of an Effect where you are using the pipe method of Observable. The root cause of the error likely lies in the implementation of your service method, specifically how it returns values. Let's break down the problematic code example to understand what's going wrong.

The Problematic Code

Here is a snippet of the effect that is throwing the error:

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

The Service Method

The method in your service looks like this:

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

Here, you might notice a couple of key problems:

The method is defined to return any, which does not enforce type checking.

The method does not return anything explicitly, so it implicitly returns undefined, leading to the TypeError when you try to call pipe on it.

Steps to Resolve

Step 1: Update the doLogin Method

Modify your doLogin method to return the Observable directly instead of subscribing within the method. Here’s how you can refactor your code:

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

Step 2: Handle Subscriptions Appropriately

In the context of NGRX, you should not manually subscribe to Observables in effects. Instead of subscribing, NGRX will manage the subscription life cycle for you. Your effect will now work as expected without explicit subscription:

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

Key Practices

Avoid using any: Always type your functions appropriately. This allows TypeScript to catch errors early and improves readability.

Understand Observables: When using Observables with NGRX, it’s crucial to grasp that they provided a way to handle data streams without immediate execution. This means you only want to have observables that other parts of your application can subscribe to.

Conclusion

The TypeError: Cannot read property 'pipe' of undefined is a common issue that many developers face when working with Angular and NGRX. By ensuring that your service methods return the correct observables without immediate subscriptions, you can effectively resolve this error. Remember to keep your return types strict to benefit from TypeScript's powerful type-checking capabilities.

By following the guidance set out in this guide, you should be well on your way to troubleshooting and overcoming this error in your Angular applications.