I define a Post class which can link or be linked to multiple posts. To do this I added a PostLink class which specifies post_to and post_from. I generated the PostLink class by rails g model post_link from_post:integer to_post:integer and of course rake db:migrate, and added belongs_to :from_post, :class_name => 'Post' belongs_to :to_post, :class_name => 'Post' to the class. And I also have has_many :post_links in my Post class. I ran rails console and Post.new.post_links and got nil printed out, which is expected. However after I save a Post using p = Post.new p.save and then run p.post_links, it prints out the following error message: SQLite3::SQLException: no such column: post_links.post_id: SELECT "post_links".* FROM "post_links" WHERE "post_links"."post_id" = 1 So anybody know why after saving it to the database post_link can not be accessed?