So the other day I was implementing what I considered a simple Rails association helper to make my life easier:
has_many :unapproved_posts,
:class_name => "Post",
:finder_sql => "SELECT posts.* from posts " +
"INNER JOIN users ON posts.user_id = users.id " +
"INNER JOIN groups ON users.group_id = groups.id " +
'WHERE (groups.id = #{id}) and ' +
'(posts.approved is NULL)'Yeah, it's a little clunky, but I needed a quick fix.
Perhaps I should have spent the time on a refactor, because this code put me in Rails hell. When displaying unapproved posts in my controller, my code iterated over a collection of Post objects. When I'd first start the server, the action would grab the association with no problems. However, every subsequent time the action runs, the Post objects I got back were missing the methods I defined in the Post model. All the attributes were there and accessible, but any methods had disappeared. Note that this only happened when accessing the posts via the association helper through the controller; doing the exact same stuff in script/console gave me no problem.
After a few hours of troubleshooting and abject frustration, I came across this ticket which seems to describe the behavior I was seeing. Note that this is a 1.2.6 application I'm working on, so the lack of resolution makes some sense. However, I needed a fix, and my friend Jon suggested I just write a method that returns the collection rather than using the helper. So running the same query with Post.find_by_sql worked fine, and since I merely needed a read-only collection, this serves my purposes.
Just wanted to drop a line in case anybody in the future runs into this. Watch out using finder_sql; it does not appear reliable. Also, if you experience this behavior in a Rails 2.0 app, let me know (less important) and reopen the ticket (very important).
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