title: ngrx - chain two store.select slices
body: <p>In my Todo Cmp I have this code</p>
  
  <pre><code>this.todoListGroup$ = this.ngrx.select(fromRoot.getTodos)
      .flatMap((todos: Todo[]) =&gt; {
          console.log(todos)
          this.todos = todos
          this.ngrx.select(fromRoot.getLastChangedTodo);
      })
      .map(lastTodo =&gt;{{
          console.log(lastTodo)
          doSomething(this.todos, lastTodo)
      })
  </code></pre>
  
  <p>When I subscribe to it I get one more console.log(lastTodo) each time todo changes. I figure that with flatmap and ngrx.select, I'm subscribing to a new Observable each time?</p>
  
  <p>with which operator can I chain two store slices?</p>
  
  <p>EDIT:</p>
  
  <p>As long as the view is in the DOM, I want to stay subscribed to todoListGroup$ since it should keep updating my view.</p>
  
  <p>My solution so far is to define a new slice in the reducer which returns the two desired properties. However, I'm still interested in which operator can effectively chain ngrx single property slices.</p>
  
  <p>Thanks!</p>