Changing $scope within an AngularJS service

Question

Changing $scope within an AngularJS service

I am currently working on an application that utilizes the Gmaps API for geolocalization. One of the challenges I faced was adding new markers based on user events. To address this, I created a service that listens to map events and adds markers when clicked. However, I encountered difficulty in modifying certain $scope properties within this service. Below is an example of the service I have developed:

climbingApp.factory('Markers', function(){
    return {
        addListener: function() {
            google.maps.event.addListener(
                map,
                'click',
                 function( e ) {
                    var marker = new google.maps.Marker({
                        position: e.latLng,
                        map: map
                    });

                }
            );
        }
    }
});

I am seeking guidance on how to retrieve the value of e.latLng and use it to update a specific $scope property. Any advice would be greatly appreciated.

javascript google-maps angularjs

Answer 1

Answer №1

According to @Ajaybeniwal, it is advised not to manipulate the scope outside of a controller. One way to handle this is by modifying addListener to accept a callback function:

climbingApp.factory('Markers', function($rootScope) {
    return {
        addListener: function(callback) {
            google.maps.event.addListener(map, 'click', function(e) {
                $rootScope.$apply(function() { callback(e); });
            });
         }
    }
});

With this change, you can now incorporate it like so within your controller:

Markers.addListener(function(e) {
    $scope.model.position = e.latLng;
});

An alternative approach is using promises instead of callbacks:

climbingApp.factory('Markers', function($rootScope, $q) {
    return {
        addListener: function() {
            var deferred = $q.defer();
            google.maps.event.addListener(map, 'click', function(e) {
                $rootScope.$apply(function() { deferred.resolve(e); });
            });
            return deferred.promise;
         }
    }
});

In this scenario, your controller would be structured in the following way:

Markers.addListener().then(function(e) {
    $scope.model.position = e.latLng;
});

Promises offer an advantage over callbacks as they can be directly bound to a view, and Angular will update the value automatically once it's ready. For more insights on this topic, refer to this post.

Lastly, it's crucial to remember that you must call $rootScope.$apply() in both instances to prompt Angular to initiate a digest cycle for proper processing. This step is necessary because Angular remains unaware of google.maps.event.addListener, therefore, it won't receive notification when the gmaps callback is executed.

Answer 2

According to @Ajaybeniwal, it is advised not to manipulate the scope outside of a controller. One way to handle this is by modifying addListener to accept a callback function:

climbingApp.factory('Markers', function($rootScope) {
    return {
        addListener: function(callback) {
            google.maps.event.addListener(map, 'click', function(e) {
                $rootScope.$apply(function() { callback(e); });
            });
         }
    }
});

With this change, you can now incorporate it like so within your controller:

Markers.addListener(function(e) {
    $scope.model.position = e.latLng;
});

An alternative approach is using promises instead of callbacks:

climbingApp.factory('Markers', function($rootScope, $q) {
    return {
        addListener: function() {
            var deferred = $q.defer();
            google.maps.event.addListener(map, 'click', function(e) {
                $rootScope.$apply(function() { deferred.resolve(e); });
            });
            return deferred.promise;
         }
    }
});

In this scenario, your controller would be structured in the following way:

Markers.addListener().then(function(e) {
    $scope.model.position = e.latLng;
});

Promises offer an advantage over callbacks as they can be directly bound to a view, and Angular will update the value automatically once it's ready. For more insights on this topic, refer to this post.

Lastly, it's crucial to remember that you must call $rootScope.$apply() in both instances to prompt Angular to initiate a digest cycle for proper processing. This step is necessary because Angular remains unaware of google.maps.event.addListener, therefore, it won't receive notification when the gmaps callback is executed.

Changing $scope within an AngularJS service

Answer №1

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