title: Access to functions of defined class from it's nested created object
body: <p>I want to access functions of class from it's nested object that's created with <code>Ext.create</code> i can't use this because it refer to created object.  </p>
  
  <pre><code>Ext.define('FM.view.HistoryProperty',{
  extend: 'Ext.grid.property.Grid',
  alias: 'widget.historyProperty',
  title: 'History',
  closable: false,
  header: true,
  layout: {
      type: 'vbox',
      align: 'left'
  },
  sortableColumns: false,
  customEditors: {
      Vehicle: Ext.create('Ext.form.ComboBox',{
          store: Ext.create('FM.store.Vehicles',{}),
          editable : false,
          queryMode: 'local',
          displayField: 'vehiclename',
          valueField: 'vehicleid',
          id: 'vehicle'
      }),
      getStartDateField: function() {
          if (!this.startDate) {
              this.startDate = Ext.create('Ext.form.DateField',{
                  format: 'y-m-d G:i',
                  value : this.yesterday(),
                  listeners: {
                      expand: {
                          fn: function(field) {
                              field.setMaxValue(this.endDate.getValue());
                          },
                          scope: this
                      }
                  }
              });
          }
          return this.startDate;
      } ,
      getEndDateField: function(){
          if(!this.endDate){
              this.endDate = Ext.create('Ext.form.DateField',{
                  format: 'y-m-d G:i',
                  selectOnFocus:true,
                  value : this.today(),
                  listeners: {
                      expand: {
                          fn: function(field){ field.setMinValue(this.startDate.getValue()); }
                      },
                      scope: this
                  }
              });
          }
          return this.endDate;
      }
  },
  yesterday: function(){
      var yesterday = new Date();
      yesterday.setDate(yesterday.getDate()-1);
      yesterday.setHours(0,0,0);
      return yesterday;
  },
  today: function(){
      var today = new Date();
      today.setHours(23,59,59);
      return today;
  },
  source: {
      "Vehicle": 'Select Vehicle',
      "getStartDateField": this.yesterday,
      "getEndDateField": this.today
  }
  </code></pre>
  
  <p>});</p>
  
  <p>I use name of defined class to access it's functions but it doesn't work.also <code>Ext.cmp('historyProperty')</code> doesn't work!.</p>