The interconnected layers of Callback Scope in AngularJS and the overarching rootScope concept

I've been working on an Angular controller to fetch records from a database and display them in a calendar. However, I'm facing an issue where the events array is returning empty. I tried using $rootScope.events as a workaround but encountered an error stating "concat is not a function of undefined." Could this be due to nested scopes causing some confusion?

Upon further investigation, I realized that the eachActivity variable is also undefined within the inner callback. It seems like there might be some fundamental knowledge missing on my end.

app.controller('Calendar', ['$scope','$rootScope','$resource','moment', function($scope, $rootScope, $resource ,moment) {

    var Activities = $resource('/api/activities');
        Activities.query(function(activities){
            $rootScope.activities = activities;
            //console.log($rootScope.activities);   
        });

    //console.log($rootScope.activities);

     var vm = this;
     var events = [];

    //setting up the calendar on rootScope so it can access Events data from other controllers
    $rootScope.calendar = new moment();

    angular.forEach($rootScope.activities, function(eachActivity){
        //console.log(eachActivity.events);
        if (eachActivity.events.length > 0){
            angular.forEach(eachActivity.events, function(eachEvent, eachActivity){
            console.log(eachEvent);    
            var entry = {
                    title: eachActivity.title,
                    type: "warning",
                    startsAt: eachEvent.startDate,
                    endsAt: eachEvent.endDate,
                    incrementBadgeTotal: true
                }

            events.concat(entry);

            }); 
        }
    });

    vm.events = events;
    console.log(vm.events);

    vm.calendarView = 'month';

    vm.viewDate = moment().startOf('month').toDate();
    vm.isCellOpen = true;

}]);

Answer №1

If you want to quickly resolve your issue, make the following adjustments:

angular.forEach(eachActivity.events, function(eachEvent, eachActivity)

should be changed to

angular.forEach(eachActivity.events, function(eachEvent)

The extra argument is unnecessary as eachActivity has already been defined in the outer loop.

Additionally, replace events.concat(entry); with events.push(entry);

Moreover, rather than defining calendar on $rootScope, it's better to create a calendar factory and inject it into the necessary controllers to access calendar data. Using $scopes for sharing data between controllers is not recommended; their main purpose is to act as a view model for binding data between views and controllers.

UPDATE (more information on creating a factory)

You can define a factory like this:

app.factory('CalendarService', [function(){
    var calendarEvents = [];  
    return {
        calendarEvents : calendarEvents
    };
}]);

In your controller:

app.controller('Calendar', ['$scope','$rootScope','$resource','moment', 'CalendarService', function($scope, $rootScope, $resource ,moment, CalendarService) {
    ...
    // instead of $rootScope.calendar = new moment 
    CalendarService.calendarEvents = events;
}]);

Simply inject CalendarService into any controller where you need the events data, and it will be accessible in the calendarEvents field.

Answer №2

There are a number of important elements at play here:

1) Utilizing the concat() method will generate a fresh array by combining the current array with the provided array(s) and/or value(s). To persist these changes for subsequent iterations, you must assign the values: events = events.concat(entry).

2) The presence of nested Angular Loops can be essential, but caution is advised when selecting naming conventions.

angular.forEach($rootScope.activities, function(eachActivity){
        angular.forEach(eachActivity.events, function(eachEvent, eachActivity)

You have used identical argument names in your loops. This practice should be avoided as it may complicate understanding the scope of the object being iterated over. I recommend ensuring that all names are distinct and clearly reflect their scope.

3) Due to the overlap in argument names, referencing title: eachActivity.title will target the second argument of the inner loop - which, in this context, represents the event's key within the forEach loop of the eachActivity.events object. Keys do not possess properties; they are always strings. Consequently, while the eachActivity variable is defined, it lacks any properties.

I suggest making adjustments to address these issues before updating your post with any advancements.

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