Скачать или смотреть How to Allow Only One Checked Checkbox in Angular Reactive Forms

Learn how to restrict checkbox selections so that only one can be checked in Angular Reactive Forms, including practical code snippets and explanations.
---
This video is based on the question https://stackoverflow.com/q/68681909/ asked by the user 'Skullkid Saquet' ( https://stackoverflow.com/u/16488093/ ) and on the answer https://stackoverflow.com/a/68682753/ provided by the user 'Devang Patel' ( https://stackoverflow.com/u/10755112/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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: Reactive form only one checked checkbox

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Allow Only One Checked Checkbox in Angular Reactive Forms

When working with forms in Angular, a common requirement is to restrict interactions to a single checkbox selection—meaning that when one checkbox is checked, all others must be unchecked. This scenario can often arise in configurations or settings where only one option can be active at a time.

In this guide, we will explore how to implement this feature using Angular's Reactive Forms. We will solve the problem by creating a method that manages the state of the checkboxes, ensuring that only one can be selected at any given time.

Understanding the Current Setup

Let's lay the groundwork by looking at the current setup of the form:

Form Structure:

A FormGroup containing input fields such as text fields, color selectors, and checkbox options.

The checkboxes have an associated default state which determines if it’s selected.

HTML Structure:

The form is displayed using an ngFor, iterating over each FormGroup.

Each checkbox is managed with a formControlName directive, linking it to its respective control.

Code Example of the Current Form

Here is a simple illustration of the setup:

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

Implementing the Logic for One Checkbox Selection

Step 1: Update the onChange Method

The existing onChange method attempts to set the checkbox value directly, which doesn't work as expected. Instead, we need to make use of the setValue() or patchValue() methods to update the form controls properly.

Updated Code

Here’s how to implement this correctly:

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

Explanation of the Logic

Loop through Controls: We loop through each control in the referentialArray.

Check Conditions: If the current index (i) is not the index of the checkbox being checked, and that checkbox is checked, we set its value to false.

Update Controls with setValue(): This guarantees we are updating the reactive form correctly, allowing Angular to detect changes.

Conclusion

By updating the onChange method to use setValue(), we ensure that only one checkbox can be selected at a time. This approach adheres to Angular’s Reactive Forms best practices, allowing for a more fluid user experience.

With these straightforward modifications, your form will now restrict users to selecting only one option out of many checkboxes. Such a user-friendly constraint enhances the overall quality of forms in your Angular applications.

Now you're equipped to tackle checkbox selections efficiently in your Angular forms. Happy coding!