elland / acts_as_relation

Multi table Inheritance for rails

Acts As Realation

Easy multi-table inheritance for rails. With acts_as_relation models inherit parent model:

• columns
• validations
• methods

Multi-table inheritance

Multi-table inheritance happens when each model in the hierarchy is a model all by itself that corresponds to its own database table and can be queried and created individually. The inheritance relationship introduces links between the child model and each of its parents (via an automatically-created has_one associations).

Example

Required columns on parent model name parent1 are

1. parent1_type
2. parent1_id

generate models

$ rails g model product name:string price:float product_type:string product_id:integer
$ rails g model pen color:string

add some validations and instance methods

class Product < ActiveRecord::Base
  validates_presence_of :name, :price
  
  def hello
    puts "Hello, My name is '#{name}', my price is $#{price}."
  end
end

pen inherits from product

class Pen < ActiveRecord::Base
  acts_as :product
end

pen inhetits products validations and colomns

p = Pen.new
p.valid? => false
p.errors => {:name=>["can't be blank"], :price=>["can't be blank"]}

pen inherits proudct methods

pen = Pen.new(:name=>"Red Pen", :color=>:red, :price=>0.99)
pen.hello => Hello, My name is 'Red Pen', my price is $0.99.

we can make queries on both models

Product.where("price <= 1")
Pen.where("color = ?", color)

---

Copyright (c) 2011 Hassan Zamani, released under the MIT license.