Solving the Issue of Ngrx Store Returning an Empty Array in Angular 10

Описание: Discover how to fix the problem of your Ngrx store returning an empty array when attempting to add items in Angular 10. Follow our step-by-step guide for an effective solution!
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This video is based on the question https://stackoverflow.com/q/64265802/ asked by the user 'jhen' ( https://stackoverflow.com/u/4318778/ ) and on the answer https://stackoverflow.com/a/64266020/ provided by the user 'jhen' ( https://stackoverflow.com/u/4318778/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the Issue of Ngrx Store Returning an Empty Array in Angular 10

When working with Ngrx in Angular 10, developers often face perplexing behaviors related to state management. One common issue is when an array intended to hold multiple items seems to reset to an empty state every time a new addition is made. This guide will discuss a specific instance where the state array does not retain its previous values, and provide a clearly defined solution to correct this behavior.

The Problem: Array Resets to an Empty State

Understanding the Scenario

Imagine you have a store with an array property (let’s call it stopps), designed to store objects. The goal is to add new items to this array each time a corresponding action is dispatched. However, users have reported that instead of appending new items, the array reverts back to an empty state.

A Typical Scenario

Initial State:

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

After Adding First Item (ID: 1):

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

After Adding Second Item (ID: 2):

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

Examination of the Reducer

The reducer, crucial to updating the state based on dispatched actions, is typically structured as follows:

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

Here, the expectation is to maintain the existing items in the stopps array while adding new items. However, developers may notice through logging that the stopps array does not behave as intended.

The Mistake: Incorrect State Initialization

After closely examining the code, it becomes evident that the issue lies in how the reducer is defined. The root of the problem is an incorrect reference to the initialUmdispoState.

Incorrect Implementation

Initially, the reducer function was incorrectly implemented as follows:

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

In this scenario, the initialUmdispoState was passed every time an action was dispatched, effectively resetting the state to its initial value (stopps: []).

The Solution: Correct State Reference

To maintain the state correctly with every action dispatched, the reducer should reference the current state:

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

Explanation of the Fix

By passing state instead of initialUmdispoState, you allow the reducer to manipulate the existing state rather than recreate the initial state on each action. Consequently, the addStopp action can correctly add new items to the stopps array, allowing your application to function as intended.

Conclusion

Errors in state management can be frustrating, particularly when developing complex applications in Angular with Ngrx. By understanding how to properly manage state references in your reducers, you can avoid situations where the state resets unexpectedly. Remember: using the correct state parameter will ensure your application functions smoothly and efficiently.

If you’ve been encountering similar issues, revisit your reducers and make sure that they maintain the previous state as intended. Happy coding!