// Set up a model to use in our Store
Ext.define('User', {
    extend: 'Ext.data.Model',
    fields: [
        {name: 'firstName', type: 'string'},
        {name: 'lastName',  type: 'string'},
        {name: 'age',       type: 'int'},
        {name: 'eyeColor',  type: 'string'}
    ]
});

var myStore = new Ext.data.Store({
    model: 'User',
    proxy: {
        type: 'ajax',
        url : '/users.json',
        reader: {
            type: 'json',
            root: 'users'
        }
    },
    autoLoad: true
});