Question

I understand how STI works, in that I have say a Post model that
contains posts on a forum and several sub-posts like
‘ordinaryUserPost’ and ‘adminUserPost’ etc.

Now, I want to define the same method in each of the sub-posts, but
the method would do something different in each case, eg

class Post < ActiveRecord::Base
end

class AdminUserPost < Post
  def background_color
    'rockstar red'
  end
end

class OrdinaryUserPost < Post
  def background_color
    'pale blue'
  end
end

(yes its a silly example). Now in my thread controller I do Post.find
(:all) and it gives me a list of posts I need to render, but they are
‘Post’ objects, not AdminUserPost or OrdinaryUserPost – so I cannot
just get my background_color method! I would have to do a find on
each type of user post separately …

Is there anyway I can do:

Post.find(:all)

And in the resultant array get a list of AdminUserPost and
OrdinaryUserPost objects instead of Post objects?

Or is there a nice way of ‘casting’ my Post objects into AdminUserPost’s and OrdinaryUserPost’s as appropriate?

EDIT:

This works as expected – provided you have a column called ‘type’ in the Post class. If your column is called something else, such as ‘post_type’ then you need to add:

self.inheritance_column = 'post_type'

In ALL the child models (AdminUserPost and OrdinaryUserPost in this example) and in the parent (Post).

Thanks,

Stephen.

Answer 1

Double check that the posts table has a column ‘type’ (string). If the AdminUserPosts and OrdinaryUserPosts are written to the table ‘posts’ and the type column is correct, you should get the subclass behavior you expect.