Question

I’m creating a message-board website using Rails. I have a Topic class and Post class.
it is easy to notice the similarity between the two classes (content, title, user_id..)

what is the best practice in Rails with this scenario?
should Topic inherit from Post? how does it work?

Answer 1

Module Mixins: just include this module on any class

Inheritance (STI): you have to use the same table for those classes

Polymorphic: you have to use a different tables for each class

In my opinion, its really hard to answer in general what is the best practice, since it really depends on the situation–in some cases you may even want to use a combination, god forbid.

I would stick with Module Mixins because its simple and flexible. If you think you’ll be double writing queries a lot because you have two separate tables, then try Inheritance (STI). From experience, definitely Polymorphic can be a headache, with a ton of gotchas if your not familiar, so probably not worth it for 2 classes.

# Heres one way to set up Inheritance (STI) on a table called 'contents'
class Content < ActiveRecord::Base
    attr_accessible :content, :title
    belongs_to :user
end

class Topic < Content
end

class Post < Content
end

Content.all             # => query topics and posts
#Post.all + Topic.all   # => query topics and posts without STI (doublewriting query)

Post.all    # => only query posts
Topic.all   # => only  topics

General Rails best practice? K eep I t S imple S tupid