Hello I have (in add_article.rhtml) a select field with some option that shows a partial in according to the selected value (though observe_fied)

Code Ruby:
<%= select_tag :article_type, options_for_select(Article::ARTICLE_TYPES) %>
<%= observe_field	:article_type,
				  :update => :articleForm,
				  :url => { :action => :show_article_form }, 
			          :with => "article_type" %>
<% end %>

and it works fine. The problem is that in the partials I need some instance variable to populate some other select, for instance:

Code Ruby:
<%= form.select :unit_id, @unit_list %>

but even if I have in my controller

Code Ruby:
def add_article
    @unit_list = Unit.find(:all, :conditions => "scope = 1", :order =>"name").map { |u| [u.name, u.id] }

I have a nill error

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.inject

related to the select above.

If I put directly the partial on add_article.rhtml it works do I guess the issue is related to the ajax call.

In which way can I use @unit_list in a partial that is called though ajax ???