SproutCore isDefault button bound to whether a group hasFirstResponder status

gistfile1.js

// ==========================================================================
// Project:   ReturnRouting - mainPage
// Copyright: @2011 My Company, Inc.
// ==========================================================================
/*globals ReturnRouting */

ReturnRouting.SelectView = SC.SelectView.extend({

  /*
    If the user presses the Return key, instead of showing the
    SelectView's popup menu, we pass the event along so that the action
    on the default button can be invoked. 
  */
  keyDown: function(evt) {
    if (evt.keyCode === SC.Event.KEY_RETURN) {
      evt.allowDefault();
      return NO;
    } else {
      return sc_super();
    }
  }
 
});

// This page describes the main user interface for your application.
ReturnRouting.mainPage = SC.Page.design({

  // The main pane is made visible on screen as soon as your app is loaded.
  // Add childViews to this pane for views to display immediately on page
  // load.
  mainPane: SC.MainPane.design({
    childViews: ['emailGroup', 'phoneGroup'],

    emailGroup: SC.WellView.design({
      layout: { left: 50, top: 50, right:50, height: 275 },
      contentView: SC.View.design({
        layout: { left:0, top:0, right:0, bottom:0 },
        childViews: ['emailTypeSelector', 'emailInput', 'addButton'],

        emailTypeSelector: ReturnRouting.SelectView.design({
          items: ['Home', 'Work'],
          layout: { left:10, top:10, width:100, height:30 },
	  acceptsFirstResponder: YES
        }),

        emailInput: SC.TextFieldView.design({
          layout: { left:110, top:10, width:100, height:30 }
        }),

        addButton: SC.ButtonView.design({
          layout: { left:10, top:50, width:60, height:30 },
          target: 'ReturnRouting',
          action: 'addEmailAddress',
          title: 'Add Email',
          isDefaultBinding: 'ReturnRouting.mainPage.mainPane.emailGroup.hasFirstResponder'
        })
      })
    }),

    phoneGroup: SC.WellView.design({
      layout: { left: 50, top: 380, right:50, height: 275 },
      contentView: SC.View.design({
        layout: { left:0, top:0, right:0, bottom:0 },
        childViews: ['phoneTypeSelector', 'phoneInput', 'addButton'],

        phoneTypeSelector: SC.SelectView.design({
          items: ['Mobile', 'Fixed'],
          layout: { left:10, top:10, width:100, height:30 }
        }),

        phoneInput: SC.TextFieldView.design({
          layout: { left:110, top:10, width:100, height:30 }
        }),

        addButton: SC.ButtonView.design({
          layout: { left:10, top:50, width:60, height:30 },
          target: 'ReturnRouting',
          action: 'addPhone',
          title: 'Add Phone',
          isDefaultBinding: 'ReturnRouting.mainPage.mainPane.phoneGroup.hasFirstResponder'
        })
      })
    })
  })
});