title: Dynamic Proxy URL for store.load() in MVC architecture with Ext JS
body: <p>I want to change the proxy of a store before (!) it is loaded. The specific problem in this case is that I do not find the right moment, when to load.</p>
  
  <p>In detail:</p>
  
  <p>I have created a MVC-model by creating a view, a controller, a model, and a store as defined by EXTJS4 architecture. The view is a grid panel. It defines the store within its own define statement:</p>
  
  <pre><code>Ext.define('P.view.MyView' ,{
      extend: 'Ext.grid.Panel',
      alias : 'widget.MyView',
      ...
      store: 'MyStore',
      ...
  }
  </code></pre>
  
  <p>When I load the store with "autoload:true" everything works fine, but of course the proxy is then static as defined in the code. When I do not use "autoload" and try to set "extraParams" and the load the store in the "initComponent" of my view like:</p>
  
  <pre><code>initComponent: function() {
      ...
      this.store.load();    
      ....
  </code></pre>
  
  <p>I get an error: Object "MyStore" has no method 'load'.</p>
  
  <p>How should I do it?</p>