Easy form/service objects and decorators

application_form.rb

# app/models/application_form.rb
module ApplicationForm
  extend ActiveSupport::Concern   

  class_methods do
    def model_name
      # Project::Form.model_name => Project.model_name
      name.deconstantize.constantize.model_name
    end
  end
end

form.rb

# app/models/project/form.rb
class Project::Form < Project
  include ApplicationForm
  
  validates :title, presence: true
end

project.rb

# app/models/project.rb
class Project < ActiveRecord::Base
end

projects_controller.rb

# app/controllers/projects_controller.rb
class ProjectsController < ApplicationController
  def new
    @project = Project::Form.new
  end
end