title: Angular HTTP - Subscribe gives unresolved variable
body: <p>I have an APIService class with the next method: </p>
  
  <pre><code>  public getRecipeIndex() : Observable&lt;Recipe[]&gt;
    {
      return this.http.get&lt;Recipe[]&gt;(this.serverURL+'recipes');
    }
  </code></pre>
  
  <p>I'm calling this method in component</p>
  
  <pre><code>  ngOnInit() {
      this.api.getRecipeIndex()
          .subscribe(
              resp =&gt; this.recipes = resp.data
          );
    }
  </code></pre>
  
  <p>and I have an error on <code>resp.data' - unresolved variable data</code>.</p>
  
  <p>All API responses have 'data' property. 
  The basic response structure from API is <code>'data' =&gt; [...]</code>.
  How can I solve this problem? I hope I can create some basic type to annotate all API calls.</p>