Take the 2-minute tour ×     1. I have a form_for mapped to a
model called List.   2. List has attributes: name, id,
receiver_id, assigner_id.   3. I want the user( or list
assigner) to be able to choose a list receiver.   4. I want the
assigner to input an e-mail, rather than the receiver's id.
1. I am not sure how to use a form to receive an e-mail address,
run a "User.find_by_email(xx).id" query using that e-mail
address, and then assign the returned id to the List's
receiver_id attribute.  Current Code:   class ListsController <
ApplicationController     before_filter :current_user     def
new       @list = List.new     def create       @list =
List.new(params[:list])       @list.assigner = @current_user
#@list.receiver = User.find_by_id(:receiver_id)
redirect_to @list     def show       @list =
List.find(params[:id])      def update  @list =
List.find(params[:id])    <%= form_for @list do |f| %>      <%=
f.label :name, 'Name'%>     <%= f.text_field :name %>      <%=
f.label :receiver_id,