How to manage the form of a model that has two foreign keys

Hi,

Basically I have two models: User and Godfather. The godfather table
has three columns:

- user_id (FK --> User)
- user_godfather_id (FK --> User)
- description (text)

Inside each model class, I am adding the following associations:

    class User < ActiveRecord::Base

      has_many :godfathers # for user_id
      has_many :godfathers, :foreign_key =>
"user_godfather_id", :class_name => "Godfather"

      accepts_nested_attributes_for :godfathers
    end

    class Godfather < ActiveRecord::Base
       belongs_to :zz_user_id, :class_name => "User"
       belongs_to :user_godfather_id, :class_name => "User"
    end

Now my question is about how to manage the edit form of this nested
attribute relationships.
Here is how my form looks like at the moment (using the
nested_form_for gem):

     <%= nested_form_for @user do |f| %>
                <%= f.fields_for :godfathers do |godfather_form| %>
                    # Here I have an ID text field but what I want
instead is
                    # to provide a username for this godfather.
                    <%= godfather_form.label :user_godfather_id %>
                    <%= godfather_form.text_field :user_godfather_id
%>

                    <%= godfather_form.label :description %>
                    <%= godfather_form.text_field :description %>

                    <%= godfather_form.link_to_remove "Remove this
godfather" %>
                 <% end %>
                <%= f.link_to_add "Add a godfather", :godfathers %>
<br/><br/>
     <%= f.submit "Update Godfathers" %>

So as I said in the comments, my goal is to be able to provide a
username for the godfather instead of an id. That username is a column
in the User table by the way.

Any idea about how I should go about it?

Thanks!

Just wanted to add a small correction for the Godfather model:

   class Godfather < ActiveRecord::Base
       belongs_to :user
       belongs_to :user_godfather, :class_name => "User"
    end