AngularJS - Injecting factory from another module into a provider - angularjs

Question

I have a factory from a separate module that I would like to inject into a provider for my module, but I keep getting unknown provider errors. What am I doing wrong?
What I would like to inject:
var angularSocketIO = angular.module('socketioModule', []);
angularSocketIO.factory('socketio', [
'$rootScope',
'addr',
function($rootScope, addr) {
var socket = io.connect(addr,{
'sync disconnect on unload': true
});
...
return socket;
}
]);
Where I am trying to inject it:
angular.module('myApp.services', ['socketioModule'])
.provider('greeter', ['socketio', function(socket) {
var salutation = 'Hello';
this.setSalutation = function(s) {
salutation = s;
}
function Greeter(a) {
this.salutation = salutation;
socket._emit('hello')
this.greet = function() {
return salutation + ' ' + a;
}
}
this.$get = function(version) {
return new Greeter(version);
};
}]);
That results in
Error: [$injector:modulerr] Failed to instantiate module myApp due to:
[$injector:modulerr] Failed to instantiate module myApp.services due to:
[$injector:unpr] Unknown provider: socketio

Answer 1

I think is because all the providers are instantiated before the factories and so a provider has to depend only on other providers.
As a way around that, I am using the injector method of angular.module to create the module.
A plunker that should do what you were trying to accomplish: http://plnkr.co/edit/g1M7BIKJkjSx55gAnuD2
Notice that I changed also the factory method. The factory method is now returning an object
with a connect method.
var angularSocketIO = angular.module('socketioModule', ['ng']);
angularSocketIO.factory('socketio', [
'$rootScope',
function($rootScope) {
return {
connect: function(addr) {
var socket = io.connect(addr, {
'sync disconnect on unload': true
});
return socket;
}
};
}]);
angular.module('myApp.services', ['socketioModule'])
.provider('greeter', [
function() {
var injector = angular.injector(['socketioModule']);
var socketio = injector.get('socketio');
var salutation = 'Hello';
this.setSalutation = function(s) {
salutation = s;
}
function Greeter(a) {
this.salutation = salutation;
socket._emit('hello');
this.greet = function() {
return salutation + ' ' + a;
};
}
this.$get = function(version) {
return new Greeter(version);
};
}
]);
var myApp = angular.module('myApp', ["myApp.services"]);

Answer 2

I think you can add dependencies via $get method in provider:
angular.module('myApp.services', ['socketioModule'])
.provider('greeter', [
function() {
...
this.$get = ['socketio', function(socket, version) {
function Greeter(a) {
this.salutation = salutation;
socket._emit('hello')
this.greet = function() {
return salutation + ' ' + a;
}
}
return new Greeter(version);
}];
}
]);