title: Angular - Integrate initial values and filters values in async pipe
body: <p>I have this function that return an Observable's list of 'streets' by passing it city id:</p>
  <pre><code>getStreetsByCityId(id: number)
  </code></pre>
  <p>And it's the template:</p>
  <pre><code>&lt;input type=&quot;text&quot; [formControl]=&quot;search&quot;&gt;
  &lt;ol&gt;
    &lt;li *ngFor=&quot;let s of list | async&quot;&gt;{{s.name}}&lt;/li&gt;
  &lt;/ol&gt;
  </code></pre>
  <p>Now, in this way i can initial the list:</p>
  <pre><code>this.list = this.mdSvc.getStreetsByCityIdObs(1)
  </code></pre>
  <p>And in this way i can handling the filter of the list:</p>
  <pre><code> this.list  = this.search.valueChanges.pipe(
    filter(val =&gt; val),
    switchMap(val =&gt; this.mdSvc.getStreetsByCityIdObs(val))
  );
  </code></pre>
  <p>What I am missing is how to do the two actions together: initial the list with values and also handling filter.
  I can not run the two actions one after one, because they will override each other.</p>
  <p>My question is actually how to both initialize the list and also support the filters together?</p>