From: zig <ziggurism@...>
Date: 2007-03-04T10:35:08+09:00
Subject: detecting associations in rails

In Rails, is there a way to list at runtime the associations (has_one,
belongs_to, etc) made for an ActiveRecord::Base model?

I would like to make my views be a little smarter about these
associations.  Currently, the scaffolding iterates through all
content_columns, which excludes the columns used for the associations,
since they end in _id.  Iterating through all columns, instead of just
content_columns, is not much better, because I don't want to see the
foreign_key either.  What I'd really like is something along the lines
of this:

<% for column in ModelA.columns %>
<%
if ModelA.content_columns.include?(column) then
  column_output = @union.send(column.name)
elsif column.name =~ /_id/ && ModelA.associations.map {|assoc|
assoc.foreign_key}.include?(column.name) then
  column_output = @union.send(ModelA.associations[:foreign_key =>
column_name])
end
%>
<p>
  <b><%= column.human_name %>:</b> <%=h column_output %>
</p>
<% end %>


OK, my logic above isn't perfect, needs some cleaning up, but
whatever.  The point is, I need a method like associations, which can
tell me what associations a model has, what their foreign keys are,
etc.

Is there any way to access that information?