notifyAndSubscribe.md

Notify and subscribe

About ?

This part is a pure custom way to manage listener in my services and factories.

The controller will execute callback when the data change.
The listener life cycle will be managed by the service.

Example

Let's take for example the current language of your application.

When you want to get or update the current language, you should do it by calling a dedicated service.
The service will have a get and set methods.

The current language value will be stored in an angular.constant file.

The MVP question here is how could I execute multiple functions from multiple controllers when this value change ?
The obvious solution is to listen for an event.

So how does it works ?

Each controller where you want to receive this event should call a method subscribe.
This methods as the $scope as first parameter and the callback function as second parameter.

The $scope is useful to automatically take care of the litener destruction directly from the service.
The callback function is the function executed when the current language change.

Instead of using a watcher in the service, we will execute a function to notify that the current language value from the angular.constant file has changed.

This function should be called on each location of the code where you edit the current language.

This notify function will send an event which is listened by the broadcast function.

Code example

function get() {
    return angular.copy(currentLanguageConstant.currentLanguage);
}

function set($newCurrentLanguage) {
    currentLanguageConstant.currentLanguage = $newCurrentLanguage;
    notify();
}

function subscribe(scope, callback) {
    var handler = $rootScope.$on('currentLanguageService:currentLanguageChanged', function() {
        callback({
            newCurrentLanguage: currentLanguageConstant.currentLanguage
        });
    });
    scope.$on('$destroy', handler);
}

function notify() {
    $rootScope.$emit('currentLanguageService:currentLanguageChanged');
}