如何按平均评分对记录进行排序?
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,一个在顶部和一个
在列表的底部。 -
如果场地3有5星评论,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目的?
感谢任何帮助,非常感谢!
编辑
场地模型
class Venue 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
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的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,必须附加<<
或将其连接到场地对象的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),然后触发回调:
@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,你可以在行w / flash[:notice]
之前添加@review.venue.update_average_rating
。
如果我理解正确,你有模型场地,有has_many:评论,每个评论都有“评级”。
我提供替代代码,例如Michael提供的代码应该更快,数百万条记录就绪,但它需要一些处理,然后添加评论(在本例中介绍),这会给你带来巨大的性能提升记录被选中,排序和显示:
创建一个将average_rating添加为float的迁移:
add_collumn :venues, :average_rating, :float, :default => 0.0, :null => false add_index :venues, :average_rating
现在,在你的控制器中:
# perhaps add paginate at the end instead of .all ... @venues = Venue.with_type(params[:venuetypes]).with_area(params[:areas]).order("average_rating DESC").all
模型更新:
class Venue < ActiveRecord::Base has_many :reviews # you'll need to create ratings for this venue via this method, so everything is atomic # and transaction safe # parameter is hash, so you can pass as many review parameters as you wish, eg # @venue.add_rating(:rating => rating, :reviewer => params[:rating][:reviewer]) # or # @venue.add_rating(params[:rating]) # :) def add_rating(rating_opts) # you can of course add as self.reviews.create(rating_opts) self.update_rating! end # let's update average rating of this venue def update_rating! s = self.reviews.sum(:rating) c = self.reviews.count self.average_rating = s.to_f / c.to_f self.save(:validate => false) # or you can use .update_attribute(:average_rating, s.to_f / c.to_f) end end
希望这可以帮助。 如果您有任何疑问,请询问。
此致,NoICE
您可以在Venue
上创建average_rating
方法,然后简单地:
@venues = Venue.with_type(params[:venuetypes]).with_area(params[:areas]).includes(:reviews).sort_by(&:average_rating).reverse
方法:
class Venue def average_rating ratings = reviews.map(&:rating) ratings.sum.to_f / ratings.size end end
如果有大量的记录或者性能是关键的,那么这个解决方案可能不是最优的,但它非常简单并且有效。
让我们假设评论是可编辑的,那么答案就不会有效。 所以我在下面做了。
class Venue < ActiveRecord::Base has_many :reviews, :dependent => :delete_all end
现在在评论模型如下。
class Venue < ActiveRecord::Base belongs_to :venue # If reviews are editable after_save :update_average_rating # If reviews are deletable before_destroy :update_average_rating private def update_average_rating s = self.venue.reviews.sum(:rating) c = self.venue.reviews.count self.venue.update_attribute(:average_rating, c == 0 ? 0.0 : s / c.to_f) end end