title: confused about ngRx way to update store
body: <p>let's assume I have an array <code>sortedNums</code> in store. It is always kept sorted.</p>
  
  <pre><code>sortedNums = [1,3,5,6,7,9];
  </code></pre>
  
  <p>Now I got a new number <code>8</code> from the server. I want to insert + sort sortedNums.
  I have following options:</p>
  
  <ol>
  <li><em>Doing it in the <code>reducers</code> itself</em>. I can do that but for complex processing, I think <code>reducers</code> won't be the right place.</li>
  <li><em>Doing it in a service method and calling it in <code>reducers</code>.</em> Will work but reducers won't stay pure.</li>
  <li><em>Doing it in <code>effect</code></em>. We don't have access to <code>sortNums</code> here. So I need to inject store and subscribe to it. This seems like an overkill to me.</li>
  </ol>
  
  <p>So my question is: what is the <code>ngRx</code> way to do store updation which requires access to existing store data.</p>