如何按平均评分对记录进行排序？

Question

我有一个场地表,我在场地索引页面上显示为局部.我还有一个评论表,其中一个场所可以有很多评论,每个评论的评分为1-5.

我正试图让索引页面上的场地显示平均评分最高且下降的场所.

控制器代码如下所示:

场地控制器

def index
    if
      @venues = Venue.with_type(params[:venuetypes]).with_area(params[:areas]).joins(:reviews).order("reviews.rating DESC")
    else
      @venues = Venue.all
    end
  end

这给出了这样的结果:

• 如果场地1有5星评价,它会显示位于列表顶部的场地.

• 如果场地2有5星评论和1星评论它显示两个部分,一个在顶部,一个
  在列表的底部.

• 如果场地3有5星评价,3星评论和1星评论它显示三个部分,一个在顶部,一个在中间,一个在列表的底部.

我只是希望每个场地有一个局部展示,但是按照平均评分排在列表中,我觉得这里有一个.average或某些遗漏的东西我怎么能实现这个？

感谢任何帮助,非常感谢!

编辑

场地模型

class Venue < ActiveRecord::Base
  attr_accessible :name, :addressline1, :addressline2, :addressline3, :addressline4, :postcode, :phonenumber, :about, :icontoppx, :iconleftpx, :area_id, :venuetype_id, :lat, :long, :venuephotos_attributes
  belongs_to :area
  belongs_to :venuetype
  has_many :reviews
  has_many :venuephotos

  accepts_nested_attributes_for :venuephotos, :allow_destroy => true

  scope :with_type, lambda { |types|
    types.present? ? where(:venuetype_id => types) : scoped }

  scope :with_area, lambda { |areas|
    areas.present? ? where(:area_id => areas) : scoped }

  def to_param
    "#{id}-#{name.gsub(/\W/, '-').downcase}"
  end

  def add_rating(rating_opts)
    @venue.add_rating(:rating => rating, :reviewer => params[:rating][:reviewer])
    self.reviews.create(rating_opts)
    self.update_rating!
  end

  def update_rating!
    s = self.reviews.sum(:rating)
    c = self.reviews.count
    self.update_attribute(:average_rating, s.to_f / c.to_f)
    self.save(:validate => false)
  end
end

用于添加评论的开发日志

Started POST "/venues/44-rating-test-5/reviews" for 127.0.0.1 at 2011-05-18 09:24:24 +0100
  Processing by ReviewsController#create as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"GZWd67b5ocJOjwKI6z9nJInBXxvQahHrjUtUpdm9oJE=", "review"=>{"rating"=>"5", "title"=>"5 star review"}, "venue_id"=>"44-rating-test-5"}
  [1m[36mVenue Load (1.0ms)[0m  [1mSELECT `venues`.* FROM `venues` WHERE (`venues`.`id` = 44) LIMIT 1[0m
  [1m[35mUser Load (0.0ms)[0m  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 3) LIMIT 1
  [1m[36mSQL (0.0ms)[0m  [1mBEGIN[0m
  [1m[35mSQL (2.0ms)[0m  describe `reviews`
  [1m[36mAREL (0.0ms)[0m  [1mINSERT INTO `reviews` (`title`, `created_at`, `updated_at`, `venue_id`, `user_id`, `rating`) VALUES ('5 star review', '2011-05-18 08:24:24', '2011-05-18 08:24:24', NULL, 3, 5)[0m
  [1m[35mSQL (27.0ms)[0m  COMMIT
  [1m[36mSQL (0.0ms)[0m  [1mBEGIN[0m
  [1m[35mAREL (0.0ms)[0m  UPDATE `reviews` SET `venue_id` = 44, `updated_at` = '2011-05-18 08:24:24' WHERE (`reviews`.`id` = 90)
  [1m[36mSQL (23.0ms)[0m  [1mCOMMIT[0m
  [1m[35mSQL (1.0ms)[0m  SELECT COUNT(*) FROM `reviews` WHERE (`reviews`.venue_id = 44)
  [1m[36mUser Load (0.0ms)[0m  [1mSELECT `users`.* FROM `users` WHERE (`users`.`id` = 3) LIMIT 1[0m
Rendered reviews/_review.html.erb (9.0ms)
Rendered reviews/create.js.erb (22.0ms)
Completed 200 OK in 220ms (Views: 56.0ms | ActiveRecord: 54.0ms)

编辑 创建审核方法(评论控制器)

def create
    @review = current_user.reviews.create!(params[:review])
    @review.venue = @venue
    if @review.save
      flash[:notice] = 'Thank you for reviewing this venue!'
      respond_to do |format|
        format.html { redirect_to venue_path(@venue) }
        format.js
      end
    else
      render :action => :new
    end
  end

Answer 1

要添加到NoICE的答案,通过挂钩:after_add和:after_remove 关联回调,您不必记住调用特殊add_rating方法.

class Venue < ActiveRecord::Base
  has_many :reviews, :after_add => :update_average_rating, :after_remove => :update_average_rating

  def update_average_rating(review=nil)
    s = self.reviews.sum(:rating)
    c = self.reviews.count
    self.update_attribute(:average_rating, c == 0 ? 0.0 : s / c.to_f)
  end

end

此外,您需要检查0的计数以防止除零.

创建审阅时,必须使用<<或附加concat到场地对象的reviews关联,以便触发回调.例如,这会将评论与场地相关联,创建评论(插入到数据库中),并触发回调:

@venue = Venue.find(params[:venue_id])
@venue.reviews << Review.new(params[:review])

这将创建审核但不会触发回调,即使venue_id是params:

Review.create(params[:review])

如果您真的想让您的操作触发回调,可以将代码更改为:

def create
  @review = Review.new(params[:review].merge({ :user => current_user, :venue => @venue })
  if @review.valid? and @venue.reviews << @review
  ...

但是,为了方便地修复它,你可以@review.venue.update_average_rating在行w /之前添加flash[:notice].