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?