Single Table Polymorphic Inheritance with ActiveRecords
Ruby on Rails warning: toplevel constant XX referenced by YY
Implementing a single table polymorphic inheritance in rails is dead easy.
Simply do
slashdot
class Fruit < ActiveRecord::Migration
def self.up
create_table :persons do |t|
t.column :type :string
t.column :shape, :string
t.timestamps
end
end
def self.down
drop_table :fruits
end
end
or if you a migrating...
class Fruit < ActiveRecord::Migration
def self.up
add_column :fruits, :type, :string
end
def self.down
remove_column :fruits, :type
end
end
Now, all you have to do is to create your sub-classes
class Fruit < ActiveRecord::Base
def calc_volume
...
end
end
class Apple < Fruit
def calc_volume
...
end
end
Don't forget to put Apple in a separate file by itself apple.rb or else ruby will spit out an unconditional warning if you reference Apple in your code with Fruit::Apple
warning: toplevel constant Fruit referenced by Fruit::Apple
Posted by Wael Chatila on May 22, 2008 10:27:00 PM PDT
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