title: ExtJS button handler not working
body: <p>My ExtJS button's handler is not invoked after clicking. Now the code looks like this.</p>
  
  <pre><code>Ext.define('EDS.view.selector.Container', {
      extend: 'Ext.form.Panel',
      alias : 'widget.selectorcontainer',
  
      title: 'Selector_V2',
      renderTo: 'input-div',
      layout: 'fit',
      height: '100%',
  
      items: [
              {
                  xtype: 'tabpanel',
                  defaults: {
                      bodyPadding: 10
                  },
              }
      ],
      buttons: [
          {
              text: 'Reset',
              handler: function(){
                  console.log("Reset");
                  this.up('form').getForm().reset();
              }
          },
          {
              text: 'Add to constrain',
              handler: this.addConstrain,
          }
      ],
  
      /*
       * Logic for button "Add to constrain"
       * 
       * Adds an entry into the constrain list describing a person, cost center or an application
       */
      addConstrain: function(button, event){
          console.log('Add_to_constrain clicked');
      }
  });
  </code></pre>
  
  <p>Originally this 'selectorcontainer' was put diretly in my app.js. But I extracted it into a stand-alone view. Before the extraction, it works perfect but now it is not working.</p>
  
  <p>BTW, I've two buttons and the first "reset" works fine. So I'm wondering if there's anything wrong with "this.addConstrain" related to scoping.</p>