【Ruby on Rails】継承している箇所でエラー「NameError in コントローラ名」

Win8.1 Rails 5.0.1 Ruby 2.3.3p222 

Rubyでこちらを参考に、検索フォームに挑戦してます。
検索フォームの実装

http://localhost:3000/products
にアクセスすると以下のようにNameErrorになります。

親クラスの名前解決が出来ていないようですが、
何か必要な設定などがあるのでしょうか？

宜しくお願い致します。

【2017/04/05追記】
参考サイトのサンプルコードまんまですが記載致します。

【コントローラ】
app\controllers\products_controller.rb

class ProductsController < ApplicationController
  before_action :set_product, only: [:show, :edit, :update, :destroy]

  # GET /products
  # GET /products.json
  def index
     @product = Search::Product.new
  end

  def search
    @product = Search::Product.new(search_params)
    @products = @product
      .matches
      .order(availability: :desc, code: :asc)
      .decorate
  end



  # GET /products/1
  # GET /products/1.json
  def show
  end

  # GET /products/new
  def new
    @product = Product.new
  end

  # GET /products/1/edit
  def edit
  end

  # POST /products
  # POST /products.json
  def create
    @product = Product.new(product_params)

    respond_to do |format|
      if @product.save
        format.html { redirect_to @product, notice: 'Product was successfully created.' }
        format.json { render :show, status: :created, location: @product }
      else
        format.html { render :new }
        format.json { render json: @product.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /products/1
  # PATCH/PUT /products/1.json
  def update
    respond_to do |format|
      if @product.update(product_params)
        format.html { redirect_to @product, notice: 'Product was successfully updated.' }
        format.json { render :show, status: :ok, location: @product }
      else
        format.html { render :edit }
        format.json { render json: @product.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /products/1
  # DELETE /products/1.json
  def destroy
    @product.destroy
    respond_to do |format|
      format.html { redirect_to products_url, notice: 'Product was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_product
      @product = Product.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def product_params
      params.require(:product).permit(:code, :name)
    end


 # 検索フォームから受け取ったパラメータ
  def search_params
    params
      .require(:search_product)
      .permit(Search::Product::ATTRIBUTES)
  end


end

【モデル】
app\models\serch\bese.rb

class Search::Base
  include ActiveModel::Model
  include ActiveModel::Validations::Callbacks

  def contains(arel_attribute, value)
    arel_attribute.matches("%#{escape_like(value)}%")
  end

  def escape_like(string)
    string.gsub(/[\\%_]/) { |m| "\\#{m}" }
  end

  def value_to_boolean(value)
    ActiveRecord::ConnectionAdapters::Column.value_to_boolean(value)
  end
end

app\models\serch\product.rb

class Search::Product < Search::Base
  ATTRIBUTES = %i(
    code
    name name_kana
    price_from price_to
    purchase_cost_from purchase_cost_to
    availability
  )
  attr_accessor(*ATTRIBUTES)

  def matches
    t = ::Product.arel_table
    results = ::Product.all
    results = results.where(contains(t[:code], code)) if code.present?
    results = results.where(contains(t[:name], name)) if name.present?
    results = results.where(contains(t[:name_kana], name_kana)) if name_kana.present?
    results = results.where(t[:price].gteq(price_from)) if price_from.present?
    results = results.where(t[:price].lteq(price_to)) if price_to.present?
    if purchase_cost_from.present?
      results = results.where(t[:purchase_cost].gteq(purchase_cost_from))
    end
    if purchase_cost_to.present?
      results = results.where(t[:purchase_cost].lteq(purchase_cost_to))
    end
    results = results.where(availability: true) if value_to_boolean(availability)
    results
  end
end

app\models\product.rb

class Product < ApplicationRecord
end