title: Is it necessary to unsubscribe from observables created by Http methods?
body: <p>Do you need to unsubscribe from Angular 2 http calls to prevent memory leak?</p>
  
  <pre><code> fetchFilm(index) {
          var sub = this._http.get(`http://example.com`)
              .map(result =&gt; result.json())
              .map(json =&gt; {
                  dispatch(this.receiveFilm(json));
              })
              .subscribe(e=&gt;sub.unsubscribe());
              ...
  </code></pre>