Rails Single Table Inheritance example

gistfile1.rb

create_table :media_items do |t|
  t.string :type, :null => false, :limit => 32
  t.string :name
  t.timestamps
end

class MediaItem < ActiveRecord::Base
  validates_presence_of :kind
end

class Post < MediaItem
 # requires a :type attribute = 'Post'
end

class Folder < MediaItem
 # requires a :type attribute = 'Folder'
end

# Create some entries
Post.new(:name => "How to Win At Poker") # translates to an INSERT INTO media_items ...
Folder.new(:name => "public_documents")

# Fetch some entries
Post.where(:name => "Travelling in Costa Rica") 
# translates to SELECT * FROM media_items where type = "Post" and name = "Travelling in Costa Rica"