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: high

Answer 1

[Rewritten with simpler solution that works fully:]

Iterating on the other answers, I have come up with the following solution for a single controller with Single Table Inheritance that works well with Strong Parameters in Rails 4.1. Just including :type as a permitted parameter caused an ActiveRecord::SubclassNotFound error if an invalid type is entered. Moreover, type is not updated because the SQL query explicitly looks for the old type. Instead, :type needs to be updated separately with update_column if it is different than what is current set and is a valid type. Note also that I've succeeded in DRYing up all lists of types.

# app/models/company.rb
class Company < ActiveRecord::Base
  COMPANY_TYPES = %w[Publisher Buyer Printer Agent]
  validates :type, inclusion: { in: COMPANY_TYPES,
    :message => "must be one of: #{COMPANY_TYPES.join(', ')}" }
end

Company::COMPANY_TYPES.each do |company_type|
  string_to_eval = <<-heredoc
    class #{company_type} < Company
      def self.model_name  # http://stackoverflow.com/a/12762230/1935918
        Company.model_name
      end
    end
  heredoc
  eval(string_to_eval, TOPLEVEL_BINDING)
end

And in the controller:

  # app/controllers/companies_controller.rb
  def update
    @company = Company.find(params[:id])

    # This separate step is required to change Single Table Inheritance types
    new_type = params[:company][:type]
    if new_type != @company.type && Company::COMPANY_TYPES.include?(new_type)
      @company.update_column :type, new_type
    end

    @company.update(company_params)
    respond_with(@company)
  end

And routes:

# config/routes.rb
Rails.application.routes.draw do
  resources :companies
  Company::COMPANY_TYPES.each do |company_type|
    resources company_type.underscore.to_sym, type: company_type, controller: 'companies', path: 'companies'
  end
  root 'companies#index'

Finally, I recommend using the responders gem and setting scaffolding to use a responders_controller, which is compatible with STI. Config for scaffolding is:

# config/application.rb
    config.generators do |g|
      g.scaffold_controller "responders_controller"
    end