Resolving the Cannot assign to read only property 'selected' Error in Angular with NGRX

Discover how to fix the error “Cannot assign to read only property 'selected' of object '[object Object]'” in Angular when using NGRX. Learn about the solution and best practices for handling data binding.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Cannot assign to read only property 'selected' of object '[object Object]'

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the Error: Cannot assign to read only property 'selected' of object '[object Object]'

In the world of Angular development, especially when working with NGRX for state management, you may come across a perplexing error: "Cannot assign to read only property 'selected' of object '[object Object]'". This issue usually manifests when you're attempting to bind your component's templates to state managed by NGRX. More specifically, this occurs when you are trying to update properties of objects that are immutable.

Let’s dive into why this error happens and how to solve it effectively.

The Problem at Hand

In your Angular component, you may have a scenario where you're rendering a list of checkboxes based on the state pulled from the NGRX store. The code snippet below illustrates the issue:

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

The corresponding TypeScript code fetches the languages from the NGRX store:

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

Understanding Read-Only State in NGRX

What is Read-Only State?

NGRX follows the principles of Redux, emphasizing immutability which means that the state should not be modified directly. All operations that require changing the state should return a new instance rather than altering an existing one. When you have strict mode enabled, all data received from the store is treated as read-only.

Why the Error Occurs

Solution: Create a Copy of the State

The solution to this problem is creating a copy of the data you receive from the NGRX store before binding it to your checkbox. By doing this, you ensure that you’re working with mutable objects that you can change freely, without running into immutability issues.

Implementation Steps

Here’s how you can modify your code:

Use the Spread Operator: Create a deep copy of each object in your array:

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

Explanation of the Code

Conclusion

By creating a copy of your store state before binding it in your template, you can easily manage the checkbox states without running into read-only errors. This approach not only solves the issue at hand but also adheres to good practices when dealing with state management in Angular applications.

Feel empowered to tackle similar issues in your development process, and remember, always strive for immutability and avoid directly modifying your store's state.

Now go ahead and implement this solution in your project to enjoy uninterrupted development with Angular and NGRX!