title: ExtJS -- submit selected checkbox values as string
body: <p>I have a checkbox group component and each checkbox value upon form submit is passed as a separate parameter like so:</p>
  
  <pre><code>mycheckboxgroup: val1
  mycheckboxgroup:val2
  mycheckboxgroup:val3
  </code></pre>
  
  <p>How can I instead submit all checkbox group values in a comma separated string?</p>
  
  <pre><code>mycheckboxgroup: val1, val2, val3
  </code></pre>
  
  <p>I tried using the <code>getSubmitData</code> method but that did not work. The values are still submitted in separate params.</p>
  
  <p>Here is a snippet of my CheckBoxGroup class:</p>
  
  <pre><code>Ext.define("MyApp.view.form.field.CheckboxGroup",{
     extend:"Ext.form.CheckboxGroup",
  
     vertical:true,
     columns:2,
     getSubmitData:function(){ 
        var fldNm = this.name; 
        return this.getValue()[fldNm].toString();
     },
  
    initComponent:function(){ 
       .....
       .....
  
       this.callParent(arguments);
    }
  
  });
  </code></pre>
  
  <p>I am using Ext 6.0.2</p>
  
  <p>Thanks</p>