Creating common controller functions

Question

How do I create some sort of utils bundle that would be accessible from all my controllers?

I have this route code in my main module:

'use strict';

angular.module('lpConnect', []).
    config(['$routeProvider', function($routeProvider) {
    $routeProvider.
        when('/home', {template: 'views/home.html', controller: HomeCtrl}).
        when('/admin', {template: 'views/admin.html', controller: AdminCtrl}).
        when('/connect', {template: 'views/fb_connect.html', controller: MainAppCtrl}).
        otherwise({redirectTo: '/connect'});
}]);

I want a function that can be common to HomeCtrl, AdminCtrl and MainAppCtrl.

How should I do it in AngularJS?

Uncouple

Answer 1

The way to define common code in angular is through Services.

You would define a new service like so :

.factory('CommonCode', function ($window) {
        var root = {};
        root.show = function(msg){
            $window.alert(msg);
        };
        return root;
    });

In your controller you would inject this service..like so

function MainAppCtrl($scope,CommonCode)
{
     $scope.alerter = CommonCode;
     $scope.alerter.show("Hello World");
}

Just include CommonCode as an argument to your controller function.. Angular will take care of injecting it for you ( Read on Dependancy Injection ..to understand what is happening here. )

Quantic

Anyone else find it.... odd that you define a service by calling the factory method? Seems like some naming improvements would go a long way to increasing approachability of the framework. – Narayan

@Narayan exactly my thoughts as I'm wrapping my head around AngularJS. factory(), value(), constant(), and service() seem to be no more than shortcuts for specific cases of provide(), which is intended to be used for defining (providing) services. I guess the docs would benefit from a pull request that puts the above sentence in large letters somewhere. – Ommatidium

To be frank, when I first started this is what confused me. Factory() generally returns a singleton, as you can see, from the above example. A service() - returns a constructor. A value() and constant() as far as I can tell generally do the same thing. And all these are wrapper ( convenience ) over provide()... – Quantic

Is the $window variable essential here? – Creech

It decouples your code from the global window object. So its much easier to test ( mock! ) . – Quantic

can you set state of the service in each controller (instead of config at module level) – Acciaccatura

e.g. i need to pass a $scope to the service, so that i dont have to pass in each function – Acciaccatura

Answer 2

Just to update previous answer (which only define what factory is), there are 3 ways to inject dependencies (define common code) in AngularJS:

• Providers
• Factories
• Services

I will not talk much about provider because it is a more laborious method for dependency injection. However, this page explains very well how they work.

---

Technically, service and factory are used for the same thing. It turns out, a service is a constructor function whereas a factory is not.

From this post:

module.service( 'serviceName', function );

When declaring serviceName as an injectable argument you will be provided with an instance of the function.

module.factory( 'factoryName', function );

When declaring factoryName as an injectable argument you will be provided with the value that is returned by invoking the function reference passed to module.factory.

---

You can use the one you prefer and obtain the same result.

Here is two codes doing exactly the same thing through service first, and then factory:

Service syntax

app.service('MyService', function () {
  this.sayHello = function () {
    console.log('hello');
  };
});

Factory syntax

app.factory('MyService', function () {
  return {
    sayHello: function () {
      console.log('hello');
    }
  }
});

Thymic