angularjs - What is the best practice for making an AJAX call in Angular.js?

Question

I was reading this article: http://eviltrout.com/2013/06/15/ember-vs-angular.html

And it said,

Due to it’s lack of conventions, I wonder how many Angular projects rely on bad practices such as AJAX calls directly within controllers? Due to dependency injection, are developers injecting router parameters into directives? Are novice AngularJS developers going to structure their code in a way that an experienced AngularJS developer believes is idiomatic?

I am actually making $http calls from my Angular.js controller. Why is it a bad practice? What is the best practice for making $http calls then? and why?

Answer 1

EDIT: This answer was primarily focus on version 1.0.X. To prevent confusion it's being changed to reflect the best answer for ALL current versions of Angular as of today, 2013-12-05.

The idea is to create a service that returns a promise to the returned data, then call that in your controller and handle the promise there to populate your $scope property.

The Service

module.factory('myService', function($http) {
   return {
        getFoos: function() {
             //return the promise directly.
             return $http.get('/foos')
                       .then(function(result) {
                            //resolve the promise as the data
                            return result.data;
                        });
        }
   }
});

The Controller:

Handle the promise's then() method and get the data out of it. Set the $scope property, and do whatever else you might need to do.

module.controller('MyCtrl', function($scope, myService) {
    myService.getFoos().then(function(foos) {
        $scope.foos = foos;
    });
});

In-View Promise Resolution (1.0.X only):

In Angular 1.0.X, the target of the original answer here, promises will get special treatment by the View. When they resolve, their resolved value will be bound to the view. This has been deprecated in 1.2.X

module.controller('MyCtrl', function($scope, myService) {
    // now you can just call it and stick it in a $scope property.
    // it will update the view when it resolves.
    $scope.foos = myService.getFoos();
});