Populate Combo box with JSON file, ExtJs 4.x.x - json

Question

Ext.define('Form', {
extend: 'Ext.data.Model',
fields: [
{name:'type', type:'String'}
]
});
var store = Ext.create('Ext.data.ArrayStore', {
model: 'Form',
autoLoad: true,
proxy: {
type: 'ajax',
url: '/test.json',
reader: {
type : 'json',
root: 'types'
}
}
});
Ext.define('DForms', {
extend: 'Ext.panel.Panel',
bodyPadding: 12,
layout : 'auto',
autoScroll : true,
items: [{
xtype:'selectcombo',
queryMode:'local',
emptyText: 'Select Condition',
store:store,
displayField: 'type',
valueField: 'type',
width : 200,
typeAhead : true
}],
});
When this loads, the selectcombo is empty, nothing gets loaded, i have searched through many sites, and can't find anything to help. Any suggestions would be great

Answer 1

The xtype you look for is combo, the store type is JsonStore because the ArrayStore will not interpret the json from the types root as you might expect. I can not simulate the ajax request here though.
Ext.onReady(function() {
Ext.define('Form', {
extend: 'Ext.data.Model',
fields: [{
name: 'type',
type: 'String'
}]
});
var store = Ext.create('Ext.data.Store', {
model: 'Form',
data: [{
type: 'Aaaaaaa'
}, {
type: 'Bbbbbb'
}, {
type: 'Ccccccccccc'
}, {
type: 'Ddddddd'
}]
});
Ext.define('DForms', {
extend: 'Ext.panel.Panel',
bodyPadding: 12,
layout: 'auto',
autoScroll: true,
items: [{
xtype: 'combo',
queryMode: 'local',
emptyText: 'Select Condition',
store: store,
displayField: 'type',
valueField: 'type',
width: 200,
typeAhead: true
}],
});
Ext.create('DForms', {
renderTo: Ext.getBody()
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/extjs/4.2.1/ext-all-debug.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/extjs/4.2.1/resources/css/ext-all.css" />

Answer 2

I think type in fields is case-sensitive. So try
fields :[{name : 'type', type : 'string'}]
If still not working, as Tejas1991 pointed out check the content of your json.