How controller call function from view controller

Hi guys,


I have a new question for you. How controller call function from view controller or view

for example:

View Controller:

Ext.define('test.view.main.MainController', {

extend: 'Ext.app.ViewController',

testfunction: function() {

//.......

}

}

Ext.define('test.controller.Root', {

extend: 'Ext.app.Controller',

//here how i can call the testfunction from viewcontroller?

}

thanks very much