A very strange problem about checkbox field

[liduqun]

The following program cann't run into this onReady function!(nothing happened!)
The checkbox field cann't be inherited?!
-------------------------------------------------------------------------------
Ext.define("PubLib.component.CheckBox", {
extend: 'Ext.form.field.CheckBox',
alias: 'widget.MyCheckBox'
});


Ext.onReady(function ()
{
Ext.create("Ext.form.Panel", {
renderTo: Ext.getBody(),

items: {
xtype: 'MyCheckBox',
inputValue: '1',
uncheckedValue: '0'
}


})
})

[mitchellsimoens]

There is no Ext.form.field.CheckBox. There is Ext.form.field.Checkbox