title: angualr2 return observable from subscribe
body: <p>Let's take a look at this example. I'm trying to return an observable value
  from subscribe, but somehow I get empty value. 
  This is scratch of my problem:</p>
  
  <pre><code>this.userService.getAll().subscribe((userCollection) =&gt; {
  
          userCollection.data.forEach((user) =&gt; {
  
              let data = {
                  id: user.id
                  domainName: this.userService.getDomain(user.id).subscribe(
                      (domain) =&gt; {
                          console.log(domain.name); // I can see this in console
                          return Observable.of(domain.name);
                      }
                  )
              };
  
              this.array.push(data);
          });
   });
  </code></pre>
  
  <p>template:<br>
     <code>&lt;div *ngFor="let values of array|async"&gt;
      {{ values.id }} 
      {{ values.domainName }} //empty
      &lt;/div&gt;</code></p>
  
  <p>Can anyone help with this please? Am I doing it in right way?</p>