AngularJS : Initialize service with asynchronous data

Question

I have an AngularJS service that I want to initialize with some asynchronous data. Something like this:

myModule.service(\'MyService\', function($http) {
            


        

Answer 1

I used a similar approach to the one described by @XMLilley but wanted to have the ability to use AngularJS services like $http to load the configuration and do further initialization without the use of low level APIs or jQuery.

Using resolve on routes was also not an option because I needed the values to be available as constants when my app is started, even in module.config() blocks.

I created a small AngularJS app that loads the config, sets them as constants on the actual app and bootstraps it.

// define the module of your app
angular.module('MyApp', []);

// define the module of the bootstrap app
var bootstrapModule = angular.module('bootstrapModule', []);

// the bootstrapper service loads the config and bootstraps the specified app
bootstrapModule.factory('bootstrapper', function ($http, $log, $q) {
  return {
    bootstrap: function (appName) {
      var deferred = $q.defer();

      $http.get('/some/url')
        .success(function (config) {
          // set all returned values as constants on the app...
          var myApp = angular.module(appName);
          angular.forEach(config, function(value, key){
            myApp.constant(key, value);
          });
          // ...and bootstrap the actual app.
          angular.bootstrap(document, [appName]);
          deferred.resolve();
        })
        .error(function () {
          $log.warn('Could not initialize application, configuration could not be loaded.');
          deferred.reject();
        });

      return deferred.promise;
    }
  };
});

// create a div which is used as the root of the bootstrap app
var appContainer = document.createElement('div');

// in run() function you can now use the bootstrapper service and shutdown the bootstrapping app after initialization of your actual app
bootstrapModule.run(function (bootstrapper) {

  bootstrapper.bootstrap('MyApp').then(function () {
    // removing the container will destroy the bootstrap app
    appContainer.remove();
  });

});

// make sure the DOM is fully loaded before bootstrapping.
angular.element(document).ready(function() {
  angular.bootstrap(appContainer, ['bootstrapModule']);
});

See it in action (using $timeout instead of $http) here: http://plnkr.co/edit/FYznxP3xe8dxzwxs37hi?p=preview

UPDATE

I would recommend to use the approach described below by Martin Atkins and JBCP.

UPDATE 2

Because I needed it in multiple projects, I just released a bower module that takes care of this: https://github.com/philippd/angular-deferred-bootstrap

Example that loads data from the back-end and sets a constant called APP_CONFIG on the AngularJS module:

deferredBootstrapper.bootstrap({
  element: document.body,
  module: 'MyApp',
  resolve: {
    APP_CONFIG: function ($http) {
      return $http.get('/api/demo-config');
    }
  }
});