Question

I have a forum table that has a “last_post_id” column, which points to the last post made in a forum. How can I include that in my main forum query so the last topic is an object that I can access?

This isn’t working, but it helps convey what I’m after

  Forum.all(
    :include    => {:posts => {:foreign_key => "last_post_id"}},
    :order      => "ancestry ASC, display_order ASC", 
  )

I’d like to be able to access the last post object using something like “forum.last_post.date”. Is this possible, what’s the cleanest solution?

The RAW sql should look something like this:

       SELECT forums.*, last_post.*
         FROM forums as forums
    LEFT JOIN posts  as last_post on last_post.id = forums.last_post_id
     ORDER BY ancestry asc, display_order asc

Answer 1

class Forum < ActiveRecord::Base
  has_many :posts
  has_one :last_post, :class_name => 'Post', :primary_key => :last_post_id
end

Forum.all(:include => [:last_post])