How to access controller variable in angularjs inside a directive?

Question

I have a upload image input in my HTML :

<div class="row">
    <div class="col-md-12">
        <div class="form-group"
            ng-class="(uploadSgnCtrl.showUploadSgnErrorMessage && uploadSgnCtrl.dataIsNullOrEmpty(uploadSgnCtrl.param)) ? 'has-error' : ''">
            <label for="signatureImage" class="required">Signature Image</label>
            <div class="input-group">
                <input type="file" id="file" name="signatureImage" 
                    class="form-control" data-file="uploadSgnCtrl.param"
                    ng-model="uploadSgnCtrl.param" file-upload>
            </div>
            <div class="row no-padding no-margin element-error-message">
                <ul class="no-padding no-margin">
                    <li ng-if="uploadSgnCtrl.dataIsNullOrEmpty(uploadSgnCtrl.param)"
                        class="no-padding no-margin">This field is Required</li>
                </ul>
            </div>
        </div>
    </div>
</div>

And in my directive a have the below code:

module.directive('fileUpload', function() {
    return {
        scope : {
            file : '=',
            accept : '=',
            showUploadSgnErrorMessage : '=' //this doesn't work
        },
        link : function(scope, el, attrs, ctrl) {
            console.log(ctrl)
            el.bind('change',
                    function(event) {
                        var files = event.target.files;
                        var file = files[0];

                        var validFormats = [ 'jpg', 'jpeg', 'png', 'JPG',
                                'JPEG', 'PNG' ];

                        var value = file.name
                        var ext = value.substr(value.lastIndexOf('.') + 1);

                        if (ext == '')
                            return;

                        if (validFormats.indexOf(ext) !== -1
                                && file.size < 2097152) {
                            scope.file = file;
                            scope.$apply();
                        } else {
                            scope.file = null;
                            console.log('file more than 2mb'); //working

                            ctrl.showUploadSgnErrorMessage = true; //not working
                            scope.showUploadSgnErrorMessage = true; //not working
                            console.log(ctrl.showUploadSgnErrorMessage); //not working
                            console.log(scope.showUploadSgnErrorMessage); //not working
                            scope.$apply();
                        }

                    });
        }
    };
});

What i want if i upload a file that is more than 2mb it will trigger the "uploadSgnCtrl.showUploadSgnErrorMessage" to true that is set in my ng-class HTML code. But above code not working(please see commented code). Though console.log('file more than 2mb') works. I get a TypeError: r is undefined next to it.

Answer 1

If you just need to access the controller scope and get / set somes value you can use $root :

scope.$root.showUploadSgnErrorMessage = true; 

I assume your uploadSgnCtrl reference is the parent controller and it has a $scope.