Calculating Mass-Assignable ActiveRecord Attributes

gistfile1.rb

class Article < ActiveRecord::Base
  # Has attributes: :title, :body, :active

  attr_protected :active
end

class Image < ActiveRecord::Base
  # Has attributes: :title, :filename, :active

  attr_accessible :title
end

a = Article.new
a.attributes                  # => [:title, :body, :active]
Article.protected_attributes  # => [:active]
Article.accessible_attributes # => [] # Where are :title and :body?

p = Photo.new
p.attributes                # => [:title, :filename, :active]
Photo.protected_attributes  # => [] # Where are :filename and :active?
Photo.accessible_attributes # => [:title]