Checkbox [ngModel] does not reflect model value when updated in (onModelChange) in angular angular

Explanation of the problem

Problem Description

The current behavior of the checkbox input with the [ngModel] binding and (ngModelChange) event handler is not functioning as expected. The checkbox only reflects the model value when it is first rendered, but then becomes equivalent to a checkbox without a binding. The logic in the onChanges function is not being run, and the view is not being updated to reflect the current value of the model.

Code Example

<input type="checkbox" [ngModel]="foo" (ngModelChange)="onChanges()" />
<input type="checkbox" (onChanges)="onChanges()" />

Environment Details

The issue has been observed on Mac OS X Sierra and is being developed using IntelliJ IDEA. The Angular version used is 2.2.0, and the code is written in TypeScript 2.0.2. The issue has been reported to occur on all browsers.

Motivation

The [ngModel] binding should always reflect the current value of the model and the logic in the onChanges function should run. The expected behavior is that the view should be updated to reflect the model’s current value. The minimal reproduction of the problem can be found at the following URL: https://plnkr.co/edit/g9niPnLsUy6wWbzm0mHi?p=preview

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Problem solution for Checkbox [ngModel] does not reflect model value when updated in (onModelChange) in angular angular

The solution to the checkbox [ngModel] not reflecting the model value when updated in (onModelChange) in Angular can be achieved through a couple of workarounds. One of the most commonly used solutions is by using a custom value accessor. This involves creating a custom component that implements the ControlValueAccessor interface and wraps the native checkbox element.

Another solution is by using the NgModelChange directive with a setTimeout function. This works by wrapping the logic inside the (ngModelChange) function in a setTimeout function, which will then wait until the end of the current JavaScript execution before executing the logic. This allows Angular to detect the change to the checkbox value before running the logic inside the (ngModelChange) function.

It’s important to note that while these solutions resolve the issue, they may cause other unintended side effects and it’s recommended to properly test and evaluate their use in different environments and applications.

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