Wiring a combo box populating two fields by means of events.

We have a 'citycombo' with store attached that has a record with the name and the state where the city resides. For example: name : 'Springfield', state : 'MA'. The selection of Springfield, MA from the city combo will populate the state field (which is freeform). How to wire the events. Flow; catch the select event, lookup the state field by means of its id 'stateId' and set the value of the field found....

   }, {
     'xtype' : 'citycombo',
     'name' : 'city',
     'fieldLabel' : 'city',
     listeners : {
      "select" : function(k, rs) {
       console.log("%o %o", k, rs);
       if (rs.length) {
        me.getComponent('iState').setValue(rs[0].get('state'));
       }
      }

     },

   }, {
     'xtype' : 'textfield',
     'id' : 'iState',
     'name' : 'state',
     'fieldLabel' : 'state',

   },