红宝石新手 . 使用baserails . 解决问题

我最近一直试图通过使用带有基础栏杆的_1743159来学习红宝石 . 一切都很好，直到我在教程中的位置，没有太多指导如何使用paperclip安装 s3 教程是为dropbox . 我很迷茫，并且已经错误了2天 . 我已经研究了很多这个问题，但由于我的知识有限，我很难理解它 . 我知道我的问题是回形针/ s3问题 . 到目前为止，我拥有所有宝石 . 有人可以和我一起工作并帮助指导我解决我的问题 . 这是我的 listings_controller.fb 文件 . 第66行给出了这个错误 .

未初始化的常量ListingsController ::列表 .

class ListingsController < ApplicationController
  before_action :set_listing, only: [:show, :edit, :update, :destroy]

  # GET /listings
  # GET /listings.json
  def index
    @listings = Listing.all
  end

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

  # GET /listings/new
  def new
    @listing = Listing.new
  end

  # GET /listings/1/edit
  def edit
  end

  # POST /listings
  # POST /listings.json
  def create
    @listing = Listing.new(listing_params)

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

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

  # DELETE /listings/1
  # DELETE /listings/1.json
  def destroy
    @listing.destroy
    respond_to do |format|
      format.html { redirect_to listings_url, notice: 'Listing was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def listing_params
      params.require(:listing).permit(:name, :description, :price, :image)
    end
end
______________Terminal_______________-
Started GET "/listings/1" for 127.0.0.1 at 2017-02-09 21:36:39 +0900
Processing by ListingsController#show as HTML
  Parameters: {"id"=>"1"}
Completed 500 Internal Server Error in 2ms (ActiveRecord: 0.0ms)

NameError（未初始化常量ListingsController :: Listing）：app / controllers / listings_controller.rb：67：在`set_listing'中渲染/Users/chrisdionne/.rvm/gems/ruby-2.3.3/gems/actionpack-5.0.1/救援/布局中的lib / action_dispatch / middleware / templates / rescues / diagnostics.html.erb渲染/Users/chrisdionne/.rvm/gems/ruby-2.3.3/gems/actionpack-5.0.1/lib/action_dispatch/middleware/ templates / rescues / _source.html.erb呈现/Users/chrisdionne/.rvm/gems/ruby-2.3.3/gems/actionpack-5.0.1/lib/action_dispatch/middleware/templates/rescues/_source.html.erb( 5.2ms）渲染/Users/chrisdionne/.rvm/gems/ruby-2.3.3/gems/actionpack-5.0.1/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb呈现/ Users / chrisdionne / . rvm / gems / ruby-2.3.3 / gems / actionpack-5.0.1 / lib / action_dispatch / middleware / templates / rescues / _trace.html.erb(2.3ms）渲染/Users/chrisdionne/.rvm/gems/ruby- 2.3.3 /宝石/ ActionPack的-5.0.1 / lib目录/ action_dispatch /中间件/模板/救援/ _request_and_response.html .erb呈现/Users/chrisdionne/.rvm/gems/ruby-2.3.3/gems/actionpack-5.0.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb(1.3ms）呈现/用户/ chrisdionne / .rvm / gems / ruby-2.3.3 / gems / actionpack-5.0.1 / lib / action_dispatch / middleware / templates / rescues / diagnostics.html.erb救援/布局（161.7ms）