title: Trouble injecting service into another service (singleton), Angular2
body: <p>I have two services, both are @Injectable. ServiceA is provided to components via the Providers array and works great everywhere. ServiceB is a singleton and is in the Providers array of its module and works great everywhere. ServiceA needs to remain not a singleton, and ServiceB needs to remain a singleton.</p>
  
  <p>My issue is that now I need to access ServiceA from ServiceB, but don't know how to access it. Seems I cannot inject a non-singleton service into a singleton.</p>
  
  <p>Everything I come across tells me to put the service in bootstrap or module declaration but as I mentioned I cannot do that as I need ServiceA to behave as a non-singleton.</p>
  
  <pre><code>// module setup
  ... providers: [ServiceB]
  
  // non-singleton
  @Injectable()
  export class ServiceA
  
  // singleton
  @Injectable()
  export class ServiceB {
    constructor(ServiceA)  // &lt;-- this is the problem area, need to get ServiceA here
  </code></pre>
  
  <p>I have tried doing something like constructor(Inject(ServiceA) serviceA) but seem to get the same errors with that</p>
  
  <blockquote>
    <p>Error: DI Error
    No provider for ServiceA!</p>
  </blockquote>
  
  <ol>
  <li>How can I "provide" a non-singleton service into a singleton service, where both are @Injectable?</li>
  </ol>