STI, one controller

Question

I'm new to rails and I'm kind of stuck with this design problem, that might be easy to solve, but I don't get anywhere: I have two different kinds of advertisements: highlights and bargains. Both of them have the same attributes: title, description and one image (with paperclip). They also have the same kind of actions to apply on them: index, new, edit, create, update and destroy.

I set a STI like this:

Ad Model: ad.rb

class Ad < ActiveRecord::Base
end

Bargain Model: bargain.rb

class Bargain < Ad
end

Highlight Model: highlight.rb

class Highlight < Ad
end

The problem is that I'd like to have only one controller (AdsController) that executes the actions I said on bargains or highlights depending on the URL, say www.foo.com/bargains[/...] or www.foo.com/highlights[/...].

For example:

• GET www.foo.com/highlights => a list of all the ads that are highlights.
• GET www.foo.com/highlights/new => form to create a new highlight etc...

How can i do that?

Thanks!

Answer 1

First. Add some new routes:

resources :highlights, :controller => "ads", :type => "Highlight"
resources :bargains, :controller => "ads", :type => "Bargain"

And fix some actions in AdsController. For example:

def new
  @ad = Ad.new()
  @ad.type = params[:type]
end

For best approach for all this controller job look this comment

That's all. Now you can go to localhost:3000/highlights/new and new Highlight will be initialized.

Index action can look like this:

def index
  @ads = Ad.where(:type => params[:type])
end

Go to localhost:3000/highlights and list of highlights will appear.
Same way for bargains: localhost:3000/bargains

etc

URLS

<%= link_to 'index', :highlights %>
<%= link_to 'new', [:new, :highlight] %>
<%= link_to 'edit', [:edit, @ad] %>
<%= link_to 'destroy', @ad, :method => :delete %>

for being polymorphic :)

<%= link_to 'index', @ad.class %>

Answer 2

fl00r has a good solution, however I would make one adjustment.

This may or may not be required in your case. It depends on what behavior is changing in your STI models, especially validations & lifecycle hooks.

Add a private method to your controller to convert your type param to the actual class constant you want to use:

def ad_type
  params[:type].constantize
end

The above is insecure, however. Add a whitelist of types:

def ad_types
  [MyType, MyType2]
end

def ad_type
  params[:type].constantize if params[:type].in? ad_types
end

More on the rails constantize method here: http://api.rubyonrails.org/classes/ActiveSupport/Inflector.html#method-i-constantize

Then in the controller actions you can do:

def new
  ad_type.new
end

def create
  ad_type.new(params)
  # ...
end

def index
  ad_type.all
end

And now you are using the actual class with the correct behavior instead of the parent class with the attribute type set.

Answer 3

I just wanted to include this link because there are a number of interesting tricks all related to this topic.

Alex Reisner - Single Table Inheritance in Rails