Ruby on Rails Single Table Inheritance Basic example
Example
First we need a table to hold our data
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :name
t.string :password
t.string :type # <- This makes it an STI
t.timestamps
end
end
end
Then lets create some models
class User < ActiveRecord::Base
validates_presence_of :password
# This is a parent class. All shared logic goes here
end
class Admin < User
# Admins must have more secure passwords than regular users
# We can add it here
validates :custom_password_validation
end
class Guest < User
# Lets say that we have a guest type login.
# It has a static password that cannot be changed
validates_inclusion_of :password, in: ['guest_password']
end
When you do a Guest.create(name: 'Bob') ActiveRecord will translate this to create an entry in the Users table with type: 'Guest'.
When you retrieve the record bob = User.where(name: 'Bob').first the object returned will be an instance of Guest, which can be forcibly treated as a User with bob.becomes(User)
becomes is most useful when dealing with shared partials or routes/controllers of the superclass instead of the subclass.
