Rails Single Table Inheritance

Remember to set the parent model with all the attributes.  There is no table for the sub models.

Ugh part one. From
http://code.alexreisner.com/articles/single-table-inheritance-in-rails.html

Overwrite the child models' model_name method:
def self.model_name
  name = "vehical"
  name.instance_eval do
    def plural;   pluralize;   end
    def singular; singularize; end
  end
  return name
end

Make the parent know it's children:

def self.select_options
  subclasses.map{ |c| c.to_s }.sort
end

@child_classes = []

def self.inherited(child)
  @child_classes << child
  super # important!
end

def self.child_classes
  @child_classes
end


Fix development env to load classes
# add to config/environments/development.rb:

%w[vehicle car truck motorcycle].each do |c|
  require_dependency File.join("app","models","#{c}.rb")
end

Also advised is to share a single controller (and resources) for the base class with all of the subclasses.

Ugh Part 2 From
http://stackoverflow.com/questions/1601739/rails-attr-accessible-does-not-work-for-type

Can't mass assign to the type attribute even if you have an attr_accessible.  So much for principle of least surprise.

Here's one option:

def type_helper   
  self.type 
end 
def type_helper=(type)   
  self.type = type
end


That's kind of nasty.

Here's another option that I hate slightly less:

# in controller
def create
   # assuming your select has a name of 'content_item_type'
   params[:content_item_type].constantize.new(params[:content_item])
end