问nil:NilClass for saas hw2的未定义方法‘hw2’

EN

NoMethodError in MoviesController#index

undefined method `keys' for nil:NilClass
Rails.root: C:/Sites/RailsProjects/hw2_rottenpotatoes

Application Trace | Framework Trace | Full Trace
app/controllers/movies_controller.rb:24:in `block in index'
app/controllers/movies_controller.rb:23:in `each'
app/controllers/movies_controller.rb:23:in `index'

class MoviesController < ApplicationController

  def show
    id = params[:id] # retrieve movie ID from URI route
    @movie = Movie.find(id) # look up movie by unique ID
  end

  def index
    redirect = false

    if params[:sort]
      @sorting = params[:sort]
    elsif session[:sort]
      @sorting = session[:sort]
      redirect = true
    end

    if redirect
      redirect_to movies_path(:sort => @sorting, :ratings => @ratings)
    end

    Movie.find(:all, :order => @sorting ? @sorting : :id).each do |mv|
      if @ratings.keys.include? mv[:rating]
        (@movies ||= [ ]) << mv
      end
    end

    session[:sort] = @sorting
    session[:ratings] = @ratings
  end

  def new
      # default: render 'new' template
  end

  def create
    @movie = Movie.create!(params[:movie])
    flash[:notice] = "#{@movie.title} was successfully created."
    redirect_to movies_path
  end

  def edit
    @movie = Movie.find params[:id]
  end

  def update
    @movie = Movie.find params[:id]
    @movie.update_attributes!(params[:movie])
    flash[:notice] = "#{@movie.title} was successfully updated."
    redirect_to movie_path(@movie)
  end

  def destroy
    @movie = Movie.find(params[:id])
    @movie.destroy
    flash[:notice] = "Movie '#{@movie.title}' deleted."
    redirect_to movies_path
  end

end