in_place_edit_field -- help please

Ok, I'm clearly missing the boat on something here, I think about how
to reference a child record (collection instance?) when using
in_place_edit_field. Meeting and AgendaItem are both models,
AgendaItem.name is the :text field I want to work with.

I have some code in my .rhtml like this (meeting has_many agenda_items)
  <h2>Agenda Items</h2>
  <% for agenda_item in @meeting.agenda_items %>
    <p> <%= agenda_item.name %></p>
  <% end %>

The controller method for this view is as follows:
  def show
    @meeting = Meeting.find(params[:id])
    @users = User.find_all
  end

This works as-expected. Now I want to be able to in_place_edit the
agenda items. I've tried several permutations, but none of them work.

this, for example:
  <h2>Agenda Items</h2>
  <% for agenda_item in @meeting.agenda_items %>
    <p> <%= in_place_editor_field :agenda_item, :name %></p>
  <% end %>

Gives me "Called id for nil, which would mistakenly be 4 -- if you
really wanted the id of nil, use object_id"

try that:
<% for agenda_item in @meeting.agenda_items %>
<% @agenda_item = agenda_item %>
   <p> <%= in_place_editor_field :agenda_item, :name %></p>
<% end %>