Angular fails to refresh Ng-class after on-change event is activated

Encountering an unusual issue with Angular. While I can trigger the desired action with ng-click, I must utilize onchange for other specific requirements.

Although my code works smoothly for other buttons that execute the same action, the upload button fails to update ng-class, despite the fact that scope.slideMenu is confirmed as true.

Additionally, I am seeking assistance in closing the menu once the user has selected an image/file.

Below is the code snippet:

HTML

    <div class="app-slide-menu"
         ng-class="{'app-menu-active': slideMenu}">

        <form class="app-set-image-file-form">
            <label class="app-file-input"
                   title="Upload Image">
                <i class="icon-enter"></i>
                <input type="file"
                       onchange="angular.element(this).scope().setImageFile(this)"
                       accept="image/*">
            </label>
        </form>
    </div>

JS

    scope.setImageFile = function (element) {
    var reader = new FileReader();

    // Converts the image to a data URL.
    reader.readAsDataURL(element.files[0]);
    scope.slideMenuToggle();

    /**
     * When the chosen image is selected, it triggers the onload function to pass the image to the whiteboardService.
     * @param event - Saves the event of the input field to get the image's data URL.
     */
    reader.onload = function (event) {
        fabric.Image.fromURL(event.target.result, function (img) {
            whiteboardService.uploadImageToCanvas(img);
        });

        // Resets the form that wraps around the file input to enable the user to add more than one of the same file.
        // NOTE: This may affect other inputs if placed inside this form
        $('.app-set-image-file-form').trigger('reset');
    };
};

And the simple toggle JS:

    scope.slideMenuToggle = function () {
    scope.slideMenu = !scope.slideMenu;
};

Answer №1

To ensure Angular recognizes changes, make use of the ngChange directive instead of the traditional onChange in JavaScript. When you stick to onChange, Angular may not detect the modifications made.

There are limited scenarios where invoking $scope.$apply() becomes necessary, especially when utilizing onChange.

Answer №2

To improve the functionality, consider developing an angular directive for a customized onchange event. Here's a sample implementation:

app.directive('customOnChange', function() {
    return {
        restrict: 'A',
        link: function(scope, element, attrs) {
            var onChangeHandler = scope.$eval(attrs.customOnChange);
            element.bind('change', onChangeHandler);
        }
    };
});

You can then implement it on your input field in the following manner:

<input type="file" custom-on-change="setImageFile" accept="image/*">

Lastly, in your controller, incorporate the following code:

$scope.setImageFile = function (element) {
    var reader = new FileReader();

    // Convert image to a data URL.
    reader.readAsDataURL(element.files[0]);
    scope.slideMenuToggle();

    /**
     * Triggered when image is selected, passing it to whiteboardService.
     * @param event - Saves the event of the input field to get the images data URL.
     */
    reader.onload = function (event) {
        fabric.Image.fromURL(event.target.result, function (img) {
            whiteboardService.uploadImageToCanvas(img);
        });

        // Reset the form wrapping the file input for multiple file selections.
        // Note: This may affect other inputs within the form.
        $('.app-set-image-file-form').trigger('reset');
    };
};

I trust this guide will be beneficial for you.

Answer №3

Hey everyone,

Unfortunately, the suggestions provided didn't work for me, but I did find a solution that resolved the bug. However, I'm still a bit confused about why it works, so I would appreciate any insights you can offer.

What I did was add a 'js-input-file' class to the input tag and include the following code to trigger a scope reset.

        var inputScope = angular.element('.js-input-file').scope();

        inputScope.$apply();

Although this solution fixed the issue, I'm puzzled as to why simply using scope.$apply(); alone didn't work. I'd love to hear your thoughts on this.

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