javascript - AngularJS global http polling service

Question

I'm building a web app using AngularJS. The app needs to poll a URL that returns JSON data and make that data available to any part of the app. From what I've read so far, my best bet is to create a service that handles the polling and keeps its own internal cache of the JSON data, and then inject the service into any part of the app that wants to consult that data. What I'm lost on is how to actually go about doing that. The closest example I've found is this question, but it appears to be creating a service that's manually called by a specific controller (which is itself tied to a given route), whereas I want something that persistently runs in the background of the app forever regardless of what part of the app is active. Is this doable, or am I taking the completely wrong approach?

Answer 1

Here my solution:

app.factory('Poller', function($http, $timeout) {
  var data = { response: {}, calls: 0 };
  var poller = function() {
    $http.get('data.json').then(function(r) {
      data.response = r.data;
      data.calls++;
      $timeout(poller, 1000);
    });      
  };
  poller();

  return {
    data: data
  };
});

(calls just to show that polling is been done)

http://plnkr.co/edit/iMmhXTYweN4IrRrrpvMq?p=preview

EDIT: As Josh David Miller suggested in comments, dependency on this service should be added in app.run block to ensure polling is done from start:

app.run(function(Poller) {});

And also moved scheduling of next poll after previous call finished. So there would not be "stacking" of calls in case if polling hangs for a long time.

Updated plunker.