Unable to programmatically uncheck a checkbox after it has been manually checked: Angular

Question

Unable to programmatically uncheck a checkbox after it has been manually checked: Angular

After being selected through the UI by clicking on the checkbox, I am encountering an issue where I cannot unselect the checkbox programmatically.

To see this behavior in action, visit the sample app, where you can click on the checkbox to select it and then click on the 'Un Check' button. Despite the property in the background switching to false, the checkbox remains selected.

Please note:

If the checkbox is not manually selected, both selecting and deselecting works as expected when done programmatically.

For further exploration, you can access the code editor here.

angular typescript checkbox

Answer 1

Answer №1

In the provided code snippet, the usage of input [checked] indicates a one-way binding.

To achieve two-way binding or to be more specific, the ability to both retrieve and set the value, you may require a setter function along with your existing logic.

If you opt not to utilize ngModel as demonstrated in the current code, consider utilizing the (change) event to update the value together with a setter function:
```
get IsChecked(): boolean {
  return this._isChecked;
}
set IsChecked(val) {
  this._isChecked = val;
}
```
The corresponding HTML implementation would be:
```
<input type="checkbox" [checked]="IsChecked" (change)="IsChecked = !IsChecked"/>
```
Alternatively, you can also make use of ngModel.

<input type="checkbox" [(ngModel)]="IsChecked"/>

which further expands to:

<input type="checkbox" [ngModel]="IsChecked" (ngModelChange)="IsChecked = !$event"/>

providing similar functionality to [checked] combined with (change) events

Answer 2

In the provided code snippet, the usage of input [checked] indicates a one-way binding.

To achieve two-way binding or to be more specific, the ability to both retrieve and set the value, you may require a setter function along with your existing logic.

If you opt not to utilize ngModel as demonstrated in the current code, consider utilizing the (change) event to update the value together with a setter function:
```
get IsChecked(): boolean {
  return this._isChecked;
}
set IsChecked(val) {
  this._isChecked = val;
}
```
The corresponding HTML implementation would be:
```
<input type="checkbox" [checked]="IsChecked" (change)="IsChecked = !IsChecked"/>
```
Alternatively, you can also make use of ngModel.

<input type="checkbox" [(ngModel)]="IsChecked"/>

which further expands to:

<input type="checkbox" [ngModel]="IsChecked" (ngModelChange)="IsChecked = !$event"/>

providing similar functionality to [checked] combined with (change) events

Answer 3

Answer №2

Modify the input in app.component.html to look like this:

<input type="checkbox" [checked]="IsChecked" (change)="onCheckedChanged()" />

and include the following code in your app.component.ts:

  onCheckedChanged() {
   this._isChecked = !this._isChecked;
  }

The Reasoning Behind the Changes:

Although you correctly bound the checked attribute to the IsChecked getter, it only updates when changes occur to IsChecked, which is why the checkboxes were not functioning properly.

When clicking on the checkbox itself, the IsChecked property does not change, hence the need to actively listen for the change event and update the IsChecked (or rather the this._isChecked) property through code.

Additionally, it is common practice in Typescript and Angular to begin class fields with a lowercase letter based on the usual conventions.

Answer 4

Modify the input in app.component.html to look like this:

<input type="checkbox" [checked]="IsChecked" (change)="onCheckedChanged()" />

and include the following code in your app.component.ts:

  onCheckedChanged() {
   this._isChecked = !this._isChecked;
  }

The Reasoning Behind the Changes:

Although you correctly bound the checked attribute to the IsChecked getter, it only updates when changes occur to IsChecked, which is why the checkboxes were not functioning properly.

When clicking on the checkbox itself, the IsChecked property does not change, hence the need to actively listen for the change event and update the IsChecked (or rather the this._isChecked) property through code.

Additionally, it is common practice in Typescript and Angular to begin class fields with a lowercase letter based on the usual conventions.

Unable to programmatically uncheck a checkbox after it has been manually checked: Angular

Answer №1

Answer №2

The Reasoning Behind the Changes:

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