database table row creation method

I have following view for user input:

<h1>Post new thing</h1>
<%= form_tag :action => 'create' %>
<p><label for="thing_title">Title</label><br/>
<%= text_field 'thing', 'title' %></p>
<p><label for="thing_description">Description</label><br/>
<%= text_area 'thing', 'description' %></p>
<p><label for="thing_email">Email</label><br/>
<%= text_field 'thing', 'email' %></p>
<%= submit_tag "Create" %>
<%= form_tag %>

... and following controller that populates data (one row) in database

def create
@thing = Thing.new(params[:thing])
end

So far it is working. But I need to add one more parameter to @thing
variable that doesn`t come from user input. It comes from another model
(:another_main_thing_id). What is the syntax for adding this parameter
to @thing variable.
Thank you!

So far it is working. But I need to add one more parameter to @thing
variable that doesn`t come from user input. It comes from another
model
(:another_main_thing_id). What is the syntax for adding this parameter
to @thing variable.

There's an accessor function created for you for each database
attribute

Fred