title: ngrx effects for a service loop
body: <p>I’m new to ngrx and trying to get the @Effect function for my ngrx store working. The code below shows how the services work if I wasn't using a ngrx store. I first make an http.get call to get a list, and then iterate on this list to get each list-item's. </p>
  
  <pre><code>export interface State {
      listItems: ItemDescription[];
      itemsData: ItemData[];
  }
  
  this.http.get('list-url').subscribe(listItems =&gt; {
      listItems.map(item =&gt; {
          this.http.get('list-item-url/' + item.id).subscribe(itemdata =&gt; {
              state.itemsData.push(itemdata);
          });
      });
  });
  </code></pre>
  
  <p>How is my @Effect function supposed to look like? Do I need to break this up into two @Effect functions, one to grab the list, another to get the items?</p>