Troubleshooting issue with Angular's two-way databinding on empty arrays

In my project, I have created a directive for a popup bubble. The buttons to be displayed in the popup are provided in an attribute as an array of objects:

JavaScript (Controller)

$scope.buttons = [{ label: 'OK' }, { label: 'Cancel' }]

The structure of the directive is as follows:

HTML

<ui-popup buttons="buttons"></ui-popup>

JavaScript (Directive)

'use strict';

angular
    .module('ui')
    .directive('uiPopup', [function () {

        return {
            replace: true,
            restrict: 'E',
            transclude: true,
            templateUrl: '/uikit/views/ui-popup.html',
            scope: {
                buttons: '=',
                anchor: '@',
                x: '@',
                y: '@'
            },
            link: function ($scope, element, attrs, ngModel) {
                ...
            }
        };
    }]);

Initially, I encountered an issue where adding buttons dynamically to an empty array using $scope.buttons.push(obj) did not reflect in the popup bubble. Surprisingly, starting with a non-empty array and then adding buttons worked perfectly fine. It raised questions about why angular data-binding breaks on an empty array and how to address this issue.

Edit

The event triggering the addition of buttons is invoked on ng-click and implemented as follows:

JavaScript (Controller)

$scope.onClick = function () {

    $scope.locked = true;
    $scope.buttons.push({ label: 'OK' });
};

Answer №1

The HTML directive was structured like this:

...
<div class="buttons" ng-if="buttons">
    <ui-button color="primary" size="small" ng-repeat="button in buttons">{{ button.label }}</ui-button>
</div>
...

In the popup, the buttons were only displayed if the variable buttons had a truthy value. It was interesting to note that the div.buttons element did not appear when buttons was empty. This was surprising because !![] evaluates to true in javascript, leading me to believe that Angular may have its own method of evaluating equality in this scenario. Even after adding a button to the array, the div did not become visible.

Upon changing the comparison to ng-if="buttons.length", which is likely how it should have been initially, the functionality started working correctly.

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