Railscookbook example error

NameError in User#list_perms

Showing app/views/user/list_perms.rhtml where line #22 raised:

uninitialized constant UserHelper::Permission

create the permission model without migration.

Also the migration for permissions table does not have a id column. This results in a bug where the update does not work for some cases. So I had to add a primary key column to the permissions table. This fixed the buggy update problem.