Folks,

I am trying to load a grid with JsonP proxy as shown in this example.
http://docs.sencha.com/ext-js/4-1/#!/example/grid/paging.html

Below is my code class :-

Code:
Ext.define('Ext.app.SampleGrid', {
    extend: 'Ext.grid.Panel',
    alias: 'widget.gridportlet',
    
    renderTopic: function(value, p, record) {
        return Ext.String.format(
            '<b><a href="http://sencha.com/forum/showthread.php?t={2}" target="_blank">{0}</a></b><a href="http://sencha.com/forum/forumdisplay.php?f={3}" target="_blank">{1} Forum</a>',
            value,
            record.data.forumtitle,
            record.getId(),
            record.data.forumid
        );
    },
    
  createModel: function() {
    	debugger;;
    	return Ext.create('Ext.data.Model', {
    		fields: [
    			'title', 'forumtitle', 'forumid', 'username',
	            {name: 'replycount', type: 'int'},
	            {name: 'lastpost', mapping: 'lastpost', type: 'date', dateFormat: 'timestamp'},
	            'lastposter', 'excerpt', 'threadid'
    		],
    		idProperty: 'threadid'
    	});
    },
    
    createProxy: function() {
    	debugger;;
    	return Ext.create('Ext.data.proxy.JsonP', {
    		url: 'http://www.sencha.com/forum/topics-browse-remote.php',
            reader: {
                root: 'topics',
                totalProperty: 'totalCount'
            },
            // sends single sort as multi parameter
            simpleSortMode: true
    	});
    },
    createStore: function() {
    	debugger;;
    	return Ext.create('Ext.data.Store', {
    		model: this.createModel,
    		proxy: this.createProxy,
    		sorters: [{
        			 property: 'lastpost',
       				 direction: 'DESC'
        	}]
    	});
    },
    initComponent: function() {
    	debugger;;
    	var pluginExpanded = true;
    	
    	Ext.apply(this, {
    		title: 'ExtJS.com - Browse Forums',
    		store: this.createStore,
	        disableSelection: true,
	        loadMask: true,
	        columns:[{
	            id: 'topic',
	            text: "Topic",
	            dataIndex: 'title',
	            flex: 1,
	            renderer: this.renderTopic,
	            sortable: false
	        },{
	            text: "Author",
	            dataIndex: 'username',
	            width: 100,
	            hidden: true,
	            sortable: true
	        },{
	            text: "Replies",
	            dataIndex: 'replycount',
	            width: 70,
	            align: 'right',
	            sortable: true
	        },{
	            id: 'last',
	            text: "Last Post",
	            dataIndex: 'lastpost',
	            width: 150,
	            renderer: this.renderLast,
	            sortable: true
	        }],
	    });
	    
	    this.callParent(arguments);
    }
});
But, I am getting the below error on console.
Uncaught TypeError: Cannot call method 'getProxy' of undefined
What I am doing wrong ?