title: ExtJS 4 Change grid store on the fly
body: <p>Is it posible to change grid's store in ExtJS 4?</p>
  
  <p>For example, i have two models:</p>
  
  <pre><code>User = Ext.define('User',{
    extend: 'Ext.data.Model',
    [...],
    hasMany: 'Product'
  });
  
  Product = Ext.define('Product',{
    extend: 'Ext.data.Model',
    [...]
  });
  </code></pre>
  
  <p>and two grids.
  The first grid is linked with Store which uses <code>User</code> model and loads nested json data from backend, like</p>
  
  <pre><code>{
    users: [{
       id: 1,
       products: [
         {id: 1},
         {id: 2}
       ]
    }, {
       id: 2,
       products: [
         {id: 3},
         {id: 4},
         {id: 5}
       ]
    }]
  }
  </code></pre>
  
  <p>All i want to get is when you click on the row in the first grid, the second grid must show products of the user, without connection to the server.
  All i know is that <code>user.products();</code> returns a <code>Ext.data.Store</code> object.
  So the idea is to change second grid's store to <code>user.products();</code>, but there is no such method <code>grid.setStore()</code> :-)</p>
  
  <p>Thanks in advance</p>