Where should I set a value to ensure all listeners are triggered?

In my AngularJS view, I have a dropdown that triggers a function when the color is changed:

<select ng-change="shop.updateSizes()" ng-model="shop.color" ng-options="color.name for color in COLORS"></select>

The updateSizes method in my controller is responsible for updating sizes based on the selected color:

shop.updateSizes = function () {
    this.sizes = this.color.sizes;
    this.updateSomethingElse(); //*

    return this;
}

I'm looking for guidance on how to initially set the color and have the updateSizes function trigger.

Additionally, I'm curious if the line labeled with a * follows best practices. Alternatively, I could add a listener in the controller object for sizes changes to call updateSomethingElse().

Answer №1

According to the provided documentation, the ng-change directive will only trigger for user input and not when the model is changed through code. This behavior is clearly outlined in the documentation for ng-change.

The directive will not execute:

- If the value returned from the $parsers transformation pipeline remains unchanged

- If the input has remained invalid and the model continues to stay null

- When the model is changed programmatically rather than through a change in the input value

It is necessary to manually call the method wherever you initialize the color.

$scope.shop.color=$scope.COLORS[0];  //selects the first value
$scope.shop.updateSizes()

Answer №2

Initializing the color value in the controller can be done with:

$scope.color = 'some-color';

When using Angular, the ng-change directives should be automatically handled, triggering the specified method in the controller.

There is no need to manually add events and listeners, as Angular is designed to handle everything seamlessly. It is recommended to refer to Angular guides for a better understanding.

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