title: Pass parameter to service constructor
body: <p>Let's suppose I have this Angular 2 service:</p>
  
  <pre><code>@Injectable()
  class Demo {
      constructor(private instanceSpecificString: string) {
      }
  }
  </code></pre>
  
  <p>Notice that its <code>constructor</code> accepts an instance-specific <code>string</code>. What I mean by that is that I want to instantiate this service multiple times and, each time it gets instantiated, I want to pass it a different <code>string</code> based on the context in which the service is instantiated.</p>
  
  <p><strong>How do I do that?</strong></p>
  
  <p>P.S. <code>string</code> is used as an example, but the parameter could easily be of type <code>number</code>, or <code>boolean</code> or even some kind of configuration <code>object</code>.</p>