Best practices to handle routes for STI subclasses in rails

Question

My Rails views and controllers are littered with redirect_to, link_to, and form_for method calls. Sometimes link_to and <

Answer 1

This way works for me ok (define this method in the base class):

def self.inherited(child)
  child.instance_eval do
    alias :original_model_name :model_name
    def model_name
      Task::Base.model_name
    end
  end
  super
end

Answer 2

Following @prathan-thananart answer, and for the multiple STI classes, you can add the following to the parent model ->

class Contact < ActiveRecord::Base
  def self.model_name
    ActiveModel::Name.new(self, nil, 'Contact')
  end
end

That will make each form with Contact data to send params as params[:contact] instead of params[:contact_person], params[:contact_whatever].

Answer 3

I was having trouble with this problem too and came by this answer on a question similar to ours. It worked for me.

form_for @list.becomes(List)

Answer shown here: Using STI path with same controller

The .becomes method is defined as mainly used for solving STI problems like your form_for one.

.becomes info here: http://apidock.com/rails/ActiveRecord/Base/becomes

Super late response, but this is the best answer I could find and it worked well for me. Hope this helps some one. Cheers!

Answer 4

You can create method that returns dummy Parent object for routing purpouse

class Person < ActiveRecord::Base      
  def routing_object
    Person.new(id: id)
  end
end

and then simply call form_for @employee.routing_object which without type will return Person class object

Answer 5

Ok, Ive had a ton of frustration in this area of Rails, and have arrived at the following approach, perhaps this will help others.

Firstly be aware that a number of solutions above and around the net suggest using constantize on client provided parameters. This is a known DoS attack vector as Ruby does not garbage collect symbols, thus allowing an attacker to create arbitrary symbols and consume available memory.

I've implemented the approach below which supports instantiation of model subclasses, and is SAFE from the contantize problem above. It is very similar to what rails 4 does, but also allows more than one level of subclassing (unlike Rails 4) and works in Rails 3.

# initializers/acts_as_castable.rb
module ActsAsCastable
  extend ActiveSupport::Concern

  module ClassMethods

    def new_with_cast(*args, &block)
      if (attrs = args.first).is_a?(Hash)
        if klass = descendant_class_from_attrs(attrs)
          return klass.new(*args, &block)
        end
      end
      new_without_cast(*args, &block)
    end

    def descendant_class_from_attrs(attrs)
      subclass_name = attrs.with_indifferent_access[inheritance_column]
      return nil if subclass_name.blank? || subclass_name == self.name
      unless subclass = descendants.detect { |sub| sub.name == subclass_name }
        raise ActiveRecord::SubclassNotFound.new("Invalid single-table inheritance type: #{subclass_name} is not a subclass of #{name}")
      end
      subclass
    end

    def acts_as_castable
      class << self
        alias_method_chain :new, :cast
      end
    end
  end
end

ActiveRecord::Base.send(:include, ActsAsCastable)

After trying various approaches for the 'sublclass loading in devlopment issue' many similar to whats suggested above, I found the only thing that worked reliably was to use 'require_dependency' in my model classes. This ensures that class loading works properly in development and causes no issues in production. In development, without 'require_dependency' AR wont know about all subclasses, which impacts the SQL emitted for matching on the type column. In addition without 'require_dependency' you can also end up in a situation with multiple versions of the model classes at the same time! (eg. this can happen when you change a base or intermediate class, the sub-classes don't always seem to reload and are left subclassing from the old class)

# contact.rb
class Contact < ActiveRecord::Base
  acts_as_castable
end

require_dependency 'person'
require_dependency 'organisation'

I also don't override model_name as suggested above because I use I18n and need different strings for the attributes of different subclasses, eg :tax_identifier becomes 'ABN' for Organisation, and 'TFN' for Person (in Australia).

I also use route mapping, as suggested above, setting the type:

resources :person, :controller => 'contacts', :defaults => { 'contact' => { 'type' => Person.sti_name } }
resources :organisation, :controller => 'contacts', :defaults => { 'contact' => { 'type' => Organisation.sti_name } }

In addition to the route mapping, I'm using InheritedResources and SimpleForm and I use the following generic form wrapper for new actions:

simple_form_for resource, as: resource_request_name, url: collection_url,
      html: { class: controller_name, multipart: true }

... and for edit actions:

simple_form_for resource, as: resource_request_name, url: resource_url,
      html: { class: controller_name, multipart: true }

And to make this work, in my base ResourceContoller I expose InheritedResource's resource_request_name as a helper method for the view:

helper_method :resource_request_name 

If you're not using InheritedResources, then use something like the following in your 'ResourceController':

# controllers/resource_controller.rb
class ResourceController < ApplicationController

protected
  helper_method :resource
  helper_method :resource_url
  helper_method :collection_url
  helper_method :resource_request_name

  def resource
    @model
  end

  def resource_url
    polymorphic_path(@model)
  end

  def collection_url
    polymorphic_path(Model)
  end

  def resource_request_name
    ActiveModel::Naming.param_key(Model)
  end
end

Always happy to hear others experiences and improvements.

Answer 6

Here is a safe clean way to have it work in forms and throughout your application that we use.

resources :districts
resources :district_counties, controller: 'districts', type: 'County'
resources :district_cities, controller: 'districts', type: 'City'

Then I have in my form. The added piece for this is the as: :district.

= form_for(@district, as: :district, html: { class: "form-horizontal",         role: "form" }) do |f|

Hope this helps.