Why are the combo elements not rendering?

Question

The following works perfectly in extjs6

Ext.define('MyThing', {

        extend: 'Ext.panel.Panel',

        items: [{
            xtype: 'combo',
            store: {
                fields: 'value',
                data: [
                        {value: 'ManagerX'},
                        {value: 'OwnerX'},
                        {value: 'FarmerX'},
                        {value: 'GovnerX'}
                    ]

            },
            displayField: 'value',
            valueField: 'value',
        }]
    })

However if I try this in extjs4 the combo elements do not render. They just render empty space. See fiddle :

https://fiddle.sencha.com/#fiddle/1i17

Why does this not work in extjs4?

Answer 1

OK, i figured it out..

The line

fields: 'value'

needs to be in an array

fields: ['value']

   Ext.define('MyThing', {
        extend: 'Ext.panel.Panel',

        items: [{
            xtype: 'combo',
            store: {
                fields: ['value'],
                data: [
                        {value: 'ManagerX'},
                        {value: 'OwnerX'},
                        {value: 'FarmerX'},
                        {value: 'GovnerX'}
                    ]

            },
            displayField: 'value',
            valueField: 'value',
        }]
    })