@ngdoc error
@name $injector:undef
@fullName Undefined Value
@description

This error results from registering a factory which does not return a value (or whose return value is undefined).

The following is an example of a factory which will throw this error upon injection:

```js
angular.module("badModule", []).
  factory("badFactory", function() {
    doLotsOfThings();
    butDontReturnAValue();
  });
```

In order to prevent the error, return a value of some sort, such as an object which exposes an API for working
with the injected object.

```js
angular.module("goodModule", []).
  factory("goodFactory", function() {
    doLotsOfThings();
    butDontReturnAValue();

    return {
        doTheThing: function methodThatDoesAThing() {
        }
    };
  });
```