Angular Services within Modules - angularjs

Question

Having difficulty injecting a service into another service. I want a service hierarchy, where I can pass/request logic to/from the parent service, for sake of brevity and encapsulation.
So for example, I have a userService, and I want the userService to manage the user's toDoList. So I created a toDoService, and I want controllers to add a toDo for the user by passing the request to the userService, which relays to the toDoService. Here's what I have:
// app.js
angular.module('myApp', [
// other dependencies...
'myApp.myServices'
]);
// services/toDoService.js
angular.module('myApp.myServices', [])
.factory('toDoService', function($http) {
getStuff = function(userId) {
// returns $http call
};
addStuff = function(userId, data) {
// returns $http call
};
});
// services/userService.js
angular.module('myApp.myServices', [])
.factory('userService',
['$http', 'toDoService', function(
$http, toDoService) {
addToDo = function(data) {
toDoService.addStuff(user.uid, data)
.then(function(success) {
// apply bindings
})
.catch(function(error) {
// display error
});
};
getToDos = function(data) {
toDoService.getStuff(user.uid)
.then(function(success) {
// apply bindings
})
.catch(function(error) {
// display error
});
};
}]);
The controller works with the userService, and code from toDoService worked when it was originally in userService. But when I create the toDoService and move that code there and encapsulate it, angular complains about toDoService.
Error: [$injector:unpr] Unknown provider: toDoServiceProvider <- toDoService <- userService
I've checked script references, and all scripts are properly included. e.g. <script src='/[..]/toDoService.js' /> etc...
So I'm wondering is it even possible to inject a service into another service within the same module? Is it an issue with my naming convention?

Answer 1

angular.module('myApp.myServices', [])
This line in userService.js defines the module myApp.services, overwriting the one that has previously been defined in toDoService.js.
Define the module only once (in a separate file). Get a reference to this previously defined module using
angular.module('myApp.myServices')
i.e. without the empty array as second argument.