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copied!<p>If I get this right, you not only want to load a <strong>polymorphic association's association</strong>, but a <strong>polymorphic association's <em>polymorphic</em> association</strong>.</p> <p>This basically means joining one defined table with another defined table through a bunch of undefined tables that come from some fields in the database.</p> <p>Since both the activity and the post are joined through a polymorphic object they both have a <code>something_id</code> and <code>something_type</code> column.</p> <p>Now I think active record doesn't let you do this out of the box but basically you want something like:</p> <pre><code>class Activity has_one :post, :primary_key => [:link_id, :link_type], :foreign_key => [:postable_id, :postable_type] end </code></pre> <p>(assuming your polymorphic association on <code>Post</code> is <code>belongs_to :postable</code>)</p> <p>That would then give you a query sort-of direct association between <code>Post</code> and <code>Activity</code> that is a very weird take on <code>habtm</code> with a 'polymorphic join table' (I just made that term up). Because both share the same polymorphicly associated object, they can be connected. Sort of like a friends-of-my-friends thing.</p> <p><strong>CAVEAT</strong>: Like I said, as far as I know, AR doesn't let you do this out of the box (though it would be awesome) but there are some gems that give you composite foreign and/or primary keys. Maybe you can find one to help you solve your problem in this way.</p>

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