angularjs - Inject service in app.config

Question

I want to inject a service into app.config, so that data can be retrieved before the controller is called. I tried it like this:

Service:

app.service('dbService', function() {
    return {
        getData: function($q, $http) {
            var defer = $q.defer();
            $http.get('db.php/score/getData').success(function(data) {
                defer.resolve(data);            
            });
            return defer.promise;
        }
    };
});

Config:

app.config(function ($routeProvider, dbService) {
    $routeProvider
        .when('/',
        {
            templateUrl: "partials/editor.html",
            controller: "AppCtrl",
            resolve: {
                data: dbService.getData(),
            }
        })
});

But I get this error:

Error: Unknown provider: dbService from EditorApp

How to correct setup and inject this service?

Answer 1

Set up your service as a custom AngularJS Provider

Despite what the Accepted answer says, you actually CAN do what you were intending to do, but you need to set it up as a configurable provider, so that it's available as a service during the configuration phase.. First, change your Service to a provider as shown below. The key difference here is that after setting the value of defer, you set the defer.promise property to the promise object returned by $http.get:

Provider Service: (provider: service recipe)

app.provider('dbService', function dbServiceProvider() {

  //the provider recipe for services require you specify a $get function
  this.$get= ['dbhost',function dbServiceFactory(dbhost){
     // return the factory as a provider
     // that is available during the configuration phase
     return new DbService(dbhost);  
  }]

});

function DbService(dbhost){
    var status;

    this.setUrl = function(url){
        dbhost = url;
    }

    this.getData = function($http) {
        return $http.get(dbhost+'db.php/score/getData')
            .success(function(data){
                 // handle any special stuff here, I would suggest the following:
                 status = 'ok';
                 status.data = data;
             })
             .error(function(message){
                 status = 'error';
                 status.message = message;
             })
             .then(function(){
                 // now we return an object with data or information about error 
                 // for special handling inside your application configuration
                 return status;
             })
    }    
}

Now, you have a configurable custom Provider, you just need to inject it. Key difference here being the missing "Provider on your injectable".

config:

app.config(function ($routeProvider) { 
    $routeProvider
        .when('/', {
            templateUrl: "partials/editor.html",
            controller: "AppCtrl",
            resolve: {
                dbData: function(DbService, $http) {
                     /*
                     *dbServiceProvider returns a dbService instance to your app whenever
                     * needed, and this instance is setup internally with a promise, 
                     * so you don't need to worry about $q and all that
                     */
                    return DbService('http://dbhost.com').getData();
                }
            }
        })
});

use resolved data in your appCtrl

app.controller('appCtrl',function(dbData, DbService){
     $scope.dbData = dbData;

     // You can also create and use another instance of the dbService here...
     // to do whatever you programmed it to do, by adding functions inside the 
     // constructor DbService(), the following assumes you added 
     // a rmUser(userObj) function in the factory
     $scope.removeDbUser = function(user){
         DbService.rmUser(user);
     }

})

Possible Alternatives

The following alternative is a similar approach, but allows definition to occur within the .config, encapsulating the service to within the specific module in the context of your app. Choose the method that right for you. Also see below for notes on a 3rd alternative and helpful links to help you get the hang of all these things

app.config(function($routeProvider, $provide) {
    $provide.service('dbService',function(){})
    //set up your service inside the module's config.

    $routeProvider
        .when('/', {
            templateUrl: "partials/editor.html",
            controller: "AppCtrl",
            resolve: {
                data: 
            }
        })
});

A few helpful Resources

• John Lindquist has an excellent 5 minute explanation and demonstration of this at egghead.io, and it's one of the free lessons! I basically modified his demonstration by making it $http specific in the context of this request
• View the AngularJS Developer guide on Providers
• There is also an excellent explanation about factory/service/provider at clevertech.biz.

The provider gives you a bit more configuration over the .service method, which makes it better as an application level provider, but you could also encapsulate this within the config object itself by injecting $provide into config like so: