validating a form with a foreign key

Hi there. I have a problem with validating a form, where is foreign key present. I have a table like this:   id   name   password   status_id

This is the way that status_id is implemented to the users table. <td><%= select_tag ('status_id', options_for_select([['-- choose one --', nil]] + @status.collect { |stat| [stat.status, stat.id]}, @user.status_id))%></td>