title: Dynamic model manipulation
body: <p>I was Googling around for best practices regarding model manipulation, and apparently, in 4.x, you had this function (<code>setField</code>, example <a href="http://www.learnsomethings.com/2012/10/05/dynamically-changing-the-model-and-store-in-extjs4-based-on-dynamic-column-headers/" rel="nofollow">here</a>).</p>
  
  <p>But in 6.x, this seems to be gone. I remember reading on the Sencha forums that dynamic models aren't really 'best practices' anyways, so is this why it seems gone in v6 ?</p>
  
  <p>I can do it on the prototype </p>
  
  <pre><code>MyModel.prototype.fields.push(Ext.create('Ext.data.field.Field', { ... }));
  </code></pre>
  
  <p>But is this the best way of doing it ?</p>
  
  <p>We're going to have grids where users can hide columns so sometimes, model validation will have to change. Also, user defined fields will either by numeric, date, string, etc. depending how what type they chose, so again validations will change dynamically.</p>
  
  <p>Thanks.</p>