The issue of AngularJS directive failing to update controller variable

After conducting an extensive search on both Google and Stack Overflow, I was unable to find a solution to the issue at hand.

So, moving forward, here is the problem I am facing:

I have created a directive that is intended to retrieve data selected in a simple input type file. When I check the data using console.log, everything appears to be working fine. However, when I attempt to monitor the value change in my controller, it never actually changes.

Below is the code for my directive:

app.directive('esFileRead', [
    function () {
        return {
            restrict: 'A',
            $scope: {
                esFileRead: '='
            },
            link: function ($scope, $elem) {
                $elem.bind('change', function (changeEvent) {
                    if (FileReader) {
                        var reader = new FileReader();
                        reader.onload = function (loadEvent) {
                            $scope.$apply(function () {
                                $scope.esFileRead= loadEvent.target.result;
                                console.log($scope.esFileRead);
                            });
                        };
                        reader.readAsDataURL(changeEvent.target.files[0]);
                    }
                    else {
                        // FileReader not supported
                    }
                });
            }
        }
    }
]);

And here is what my controller looks like:

app.controller('MainController', [
    '$rootScope',
    '$scope',
    'DataManagementService',
    function ($rootScope, $scope, DataManagementService) {
        $scope.importFile = "";

        $scope.$watch('importFile', function (newValue, oldValue) {
            console.log(newValue);
            if(newValue && newValue !== oldValue) {
                DataManagementService.importData(newValue);
            }
        });

    }
]);

This is how my view is set up:

<input id="btnImport" type="file" es-file-read="importFile"/>

Answer №1

It appears that a typo was made in the Directive Definition Object, where $scope should actually be scope.


To enhance your current approach, I recommend avoiding the use of a watcher in the parent controller method. Instead, consider passing a callback to the directive and invoking it once the reader object is loaded. This will result in an isolated scope as shown below:

restrict: 'A',
scope: {
    callback: '&'
},

Create a new method in the controller to handle passing file data:

$scope.importData = function(data) {
    DataManagementService.importData(newValue);
});

Ensure that the callback method is correctly passed on to the directive element:

<input id="btnImport" type="file" es-file-read callback="importData(data)"/>

Execute the method accurately within the directive code:

reader.onload = function (loadEvent) {
    $scope.$apply(function () {
        $scope.esFileRead= loadEvent.target.result;
        $scope.callback({ item: $scope.esFileRead });
    });
};

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