Example: links in ViewModel.

Ext.define('SchoolApp.view.student.StudentMaster', {
    extend: 'Ext.form.Panel',
    requires: ['SchoolApp.view.student.StudentViewModel'],

    alias: 'widget.StudentMasterForm',
    config: {},

    viewModel: { type: 'StudentViewModel' },

    bind: {
        title: '{title} Information'
    },

    constructor: function (config) {
        return this.callParent(arguments);
    },

    initComponent: function () {

        Ext.apply(this, {

            collapsible: true,
            bodyPadding: '5',
            buttonAlign: 'center',
            border: false,
            layout: 'anchor',
            defaults: {
                anchor: '100%'

            },
            items: [{
                fieldLabel: 'Id',
                xtype: 'textfield',
                name: 'Id',
                readOnly: true,
                width: '35',
                bind: {
                    value: '{theStudent.Id}'
                }
            },
            {
                xtype: 'textfield',
                fieldLabel: 'First Name',
                bind: {
                    value: '{theStudent.firstName}'
                }
            },
            {
                xtype: 'textfield',
                fieldLabel: 'Last Name',
                bind: {
                    value: '{theStudent.lastName}'
                }
            },
            {
                xtype: 'displayfield',
                fieldLabel: 'Full Name',
                bind: {
                    value: '{fullName}'
                }
            },
            {
                xtype: 'datefield',
                fieldLabel: 'DoB',
                name: 'birthDate',
                bind: {
                    value: '{theStudent.birthDate}'
                }
            },
            {
                xtype: 'container',
                layout: 'hbox',
                items: [
                    {
                        xtype: 'fieldcontainer',
                        flex: 1,
                        layout: 'hbox',
                        items: [
                            {
                                xtype: 'fieldcontainer',
                                flex: 1,
                                layout: 'anchor',
                                items: [
                                {
                                    xtype: 'textfield',
                                    fieldLabel: 'Address1',
                                    name: 'address1',
                                    anchor: '95%',
                                    bind: {
                                        value: '{theStudent.address1}'
                                    }
                                },
                                {
                                    xtype: 'textfield',
                                    fieldLabel: 'Address2',
                                    name: 'address2',
                                    anchor: '95%',
                                    bind: {
                                        value: '{theStudent.address2}'
                                    }
                                }
                                ]
                            },
                            {
                                xtype: 'fieldcontainer',
                                flex: 1,
                                layout: 'anchor',
                                items: [
                                {
                                    xtype: 'textfield',
                                    fieldLabel: 'City',
                                    name: 'city',
                                    anchor: '100%',
                                    bind: {
                                        value: '{theStudent.city}'
                                    }
                                },
                                {
                                    xtype: 'textfield',
                                    fieldLabel: 'State',
                                    name: 'state',
                                    anchor: '100%',
                                    bind: {
                                        value: '{theStudent.state}'
                                    }
                                }
                                ]
                            }]
                    }]
            }],
            buttons: [
                { text: 'Save', itemID: 'btnSave' },
                { text: 'Reset' }
            ]
        });
        this.callParent(arguments);
    }
});

Ext.define('SchoolApp.view.student.StudentViewModel', {
    extend: 'Ext.app.ViewModel',
    alias:'viewmodel.StudentViewModel',
    data: {
        title: 'Student'
    },
    formulas: {
        fullName: function(get){
            return get('theStudent.firstName') + ' ' + get('theStudent.lastName');
        }
    },
    links: {
        theStudent: {
            type: 'Student',
            id:5
        }
    }
});

Ext.define('SchoolApp.model.Student', {
    extend: 'Ext.data.Model',
    idProperty: 'Id',

    schema: {
        namespace: 'SchoolApp.model',
        proxy: {
            type:'ajax',
            api: {
                read: '/ExampleService.svc/students/'
            },
            reader:{
                type:'json',
                rootProperty:'data'
            }
        }
    },
    fields: [
        { name: 'Id', type: 'int' },
        { name: 'firstName', type: 'string' },
        { name: 'middleName', type: 'string' },
        { name: 'lastName', type: 'string' },
        { name: 'birthDate', type: 'date' },
        { name: 'address1', type: 'string' },
        { name: 'address2', type: 'string' },
        { name: 'city', type: 'string' },
        { name: 'state', type: 'string' }
    ]
    
});

Ext.application({
    name: 'SchoolApp',
    autoCreateViewport: false,
    views: ['SchoolApp.view.student.StudentMaster'],
    controllers: [],
    requires: ['SchoolApp.model.Student', 'SchoolApp.view.student.StudentViewModel'],

    launch: function () {

        Ext.create('Ext.container.Viewport', {
            layout: 'border',
            items: [
                {
                    xtype: 'StudentMasterForm',
                    region: 'center'
                }
            ]
        });
    }
});

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <link href="http://cdn.sencha.com/ext/gpl/5.1.0/packages/ext-theme-neptune/build/resources/ext-theme-neptune-all.css" rel="stylesheet" />
    <script src="http://cdn.sencha.com/ext/gpl/5.1.0/build/ext-all-debug.js"></script>
    <script src="http://cdn.sencha.com/ext/gpl/5.1.0/packages/ext-theme-neptune/build/ext-theme-neptune.js"></script>
    
    <script src="app.js"></script>
</head>
<body>
</body>
</html>