Rails Model Inheritance

Question

If I have a User and I want to make different types of users, say just normal users with only an email and subscribers who have a website field, how would I make subscribers inherit everything from Users with just an added field?

Answer 1

You would need to create a table with all of the fields, as well as specify a type column. i.e

create_table :users do |t|   t.string :email   t.string :website   t.string :type end 

Then you can have classes like

Class User < ActiveRecord::Base  Class Subscriber < User 

A subscriber will inherit everything from the Users model. The type column is there so that you can distinguish from the different models. For instance using

Subscriber.all  

Will only get subscribers, where as if you did not use the 'type' column it would also find users too.

Answer 2

You want single table inheritance, described at the link by Alex Reisner. STI uses a single table to represent multiple models that inherit from a base model. In the Rails world, the database schema has a column which specifies the type of model represented by the row. Adding a column named type in a database migration has Rails infer the table uses STI, although the column can be an arbitrary name if you specify the name in the data model (see the class method 'inheritance_column'). Note that this makes type a reserved word.