Monitoring variables in AngularJS services

Hey, I'm having some trouble with this issue. I've searched everywhere for a solution, but couldn't find one, despite there being similar questions out there.

Basically, I have a class and I only need one instance of it, so I created a service for it:

services.factory('PlayerService', ->
     new Player()
)

The class is related to a player and I'm trying to figure out how to update my view when the song changes.

Check out this simplified demo on Plunker that demonstrates the problem: http://plnkr.co/edit/L3WndT

Here's what I've attempted based on this question, but none of the solutions are working for me.

View

<div ng-controller="PlayerController">
    {{ player.currentSong }}
</div>

First approach

PlayerController = ($scope, PlayerService) ->
    $scope.player = PlayerService
    return

Second approach

PlayerController = ($scope, PlayerService) ->
    $scope.$watch(
        'myApp.services.PlayerService'
        (newval, oldval) ->
            $scope.currentSong = newval
        true
    )
    return

Answer №1

When faced with a situation where you are working with an external service that updates regularly but does not offer a way to listen for updates (as shown in your Plunker example), one approach is to periodically check for updates and ensure that the scope stays updated.

Here is a link to the Plunker example: http://plnkr.co/edit/PJpQ2a?p=preview

It's important to note that the polling method does not necessarily have to explicitly update the scope. Angular automatically watches the expression 'serviceClass.prop' included in the view. The $timeout service activates a digest cycle, which in turn triggers the watch listener when the expression changes, leading to an update in the view.

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