Need some help with SC.SelectView

I'm trying to understand how it works. I have view:

roleSwitch: SC.SelectView.design({
                      layout: {top:38, height: 20, width: 256 },
                      items:  [{ title: 'a', isEnabled: YES, checkbox: NO },
                  开发者_如何学编程             { title: 'b', isEnabled: YES, checkbox: NO }],
                              itemTitleKey: 'title',
                              themeName: 'role', 
                              showCheckbox: NO

                      })

I can't find any other information about SelectView. How i can pre-select item, where selection goes, why do I get an error each time when i make a selection?

Selection: Lets say you have this:

MyApp.roleController = SC.ObjectController({
  selectedRoleId: 1;
})

Then in your view:

roleSwitch: SC.SelectView.design({
                      layout: {top:38, height: 20, width: 256 },
                      items:  [{ title: 'a', isEnabled: YES, checkbox: NO, roleId: 1 },
                               { title: 'b', isEnabled: YES, checkbox: NO, roleId: 2 }],
                              itemTitleKey: 'title',
                              themeName: 'role', 
                              showCheckbox: NO,
                              itemValueKey: 'roleId',
                              valueBinding: 'MyApp.roleController.selectedRoleId'

                      })

Your selection will be bound to the 'selectedRoleId' of the roleController