Rails 4 ActiveRecord按关联计数排序

Question

我想要显示

的内容

例如：

recipe.user.name 
recipe.name
recipe.picture
recipe.created_at

按

排序

recipe.likes.count

控制器：

@recipes_by_likes = Recipe.likes_count.paginate(page: params[:page])

型号：

Recipe has_many :likes

和

Like belongs_to :recipe

范围：

scope :likes_count, -> { 
  select('recipes.*, COUNT(likes.id) AS likes_count').
  joins(:likes).
  order('likes_count DESC')
}

但是这给了我

SELECT  recipes.*, COUNT(likes.id) AS likes_count 
FROM "recipes" 
INNER JOIN "likes" ON "likes"."recipe_id" = "recipes"."id"  
ORDER BY "recipes"."created_at" DESC, likes_count DESC 
LIMIT 30 OFFSET 0

只返回1（错误）结果。

Answer 1

1。查询

你不应该按照document.getElementsByClassName(name)计算喜欢，因为它总是唯一的，并且总是返回1，而不是id，这与某个食谱相关的喜欢相同。

recipe_id

2。计数器缓存方法

您也可以使用scope :likes_count, -> { select('recipes.*, COUNT(likes.recipe_id) AS likes_count') .joins(:likes) .group('recipes.id') .order('likes_count DESC') }

counter_cache

并向class Like < ActiveRecord::Base belongs_to :recipe, counter_cache: true end 模型

添加一列

Recipe