I'm trying to pass a callback function from a controller to a directive.

Here's the callback function code:

$scope.onImageSelect = function(image) {

    alert('SET');

    $scope.card.image = image;

};

Directive usage:

<google-image-search callback=onImageSelect />

Directive code:

ngmod.directive('directive', function() {

    return {

        templateUrl: '/templates/template.html',

        scope: {

            callback: '&'

        }

    }

});

Callback usage in template:

<a data-ng-click=callback(url)></a>

However, this gives me the following error:

TypeError: Cannot use 'in' operator to search for 'onImageSelect'

I've seen a lot of similar questions, but could not understand where am I wrong.