Example base controller using STI.

sti_forms_controller.rb

class FormsController < ApplicationController
  before_action :set_form, only: [:show, :edit, :update, :destroy, :embed, :customize]

  # GET /forms
  # GET /forms.json
  def index
    @forms = skope.newest_first
    respond_to do |format|
      format.html
      format.json { render json: @forms }
    end
  end

  # GET /forms/1
  # GET /forms/1.json
  def show; end

  # GET /forms/new
  def new
    @form = skope.new
  end

  # GET /forms/1/edit
  def edit; end
  # ...

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_form
      @form = FormPresenter.new(skope.find_by!(slug: params[:id]))
    end
  
    def permitted_params
      [
        :user_id,
        :headline,
        :body
        # :etc...
      ]
    end
  
    # Never trust parameters from the scary internet, only allow the white list through.
    def form_params
      params.require(:form).permit(permitted_params)
    end

    def skope
      raise "skope must be implemented in STI subclass"
    end
end