title: Restangular: Error: Unknown provider
body: <p>I want to inject Restangular in my app to communicate with via REST. </p>
  
  <p>So, here I am know with an error:</p>
  
  <pre><code>Error: [$injector:unpr] Unknown provider: RestangularProvider &lt;- Restangular &lt;- Api
  </code></pre>
  
  <p><code>Api</code> is my own module here. What I'm doing:</p>
  
  <blockquote>
    <ol>
    <li>Creating a main module called Dashboard</li>
    <li>Creating a submodule called API</li>
    </ol>
  </blockquote>
  
  <p>Now I want to use Restangular, but couldn't figure out how Angular is managing the dependencies...</p>
  
  <p>Here is my sub-module where I inject Restangular:</p>
  
  <pre><code>angular.module( 'dashboard.api', ['restangular']).factory('Api', ['$http', 'Config', 'Restangular', function($http, Config, Restangular) {
  </code></pre>
  
  <p>My main module, Dashboard, doesn't need to inject Restangular, right?</p>
  
  <pre><code>angular.module( 'dashboard', [ 'dashboard.api'])
  </code></pre>
  
  <blockquote>
    <p>How is the injection-depency working within submodules? How can I
    integrate Restangular in my app?</p>
  </blockquote>
  
  <p>EDIT: Source file is included:
  <img src="https://i.stack.imgur.com/gC1rU.png" alt="enter image description here"></p>