How do I define texfield validator scope? I define validator in controller with this code:

PHP Code:
this.editView.getRegNumberTextField().validator  this.regNumberValidator;
regNumberValidator:function (input) {
//validation here

But in this case the scope in regNumberValidator function is RegNumberTextField. I want it to be the Controller scope. I tried Ext.apply with {scope:this} but it didn't help. There should be some way to define the scope, like in on('event',handler, scope) statement.