counter_cache 和 has_many :through [英] counter_cache with has_many :through
本文介绍了counter_cache 和 has_many :through的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我刚刚创建了一个 counter_cache 字段,控制器看起来像这样.
I just created a counter_cache field and the controller looks like this.
@users = User.where(:sex => 2).order('received_likes_count')
User.rb 中的关联是
The association in User.rb is
has_many :received_likes, :through => :attachments, :source => :likes, :dependent => :destroy
问题是 counter_cache 是在 Like.rb 的belong_to 中声明的,我不知道如何告诉它是为了 has_many :through 关联.
Problem is that counter_cache is declared in the belong_to of Like.rb and I don't know how to tell it that is for the has_many :through association.
belongs_to :user, :counter_cache => :received_likes
推荐答案
您有上一个
class Product
has_and_belongs_to_many :categories
end
class Category
has_and_belongs_to_many :products
end
和迁移
class CreateCategoriesProducts < ActiveRecord::Migration
def change
create_table :categories_products, id: false do |t|
t.references :category
t.references :product
end
add_index :categories_products, [:category_id, :product_id]
end
end
现在全部改为
class Product
has_many :categories_products, dependent: :destroy
has_many :categories, through: :categories_products
end
class Category
has_many :categories_products, dependent: :destroy
has_many :products, through: :categories_products
end
和新的
class CategoriesProduct < ActiveRecord::Base
# this model uses table "categories_products" as it is
# column products_count is in the table "categories"
belongs_to :category, counter_cache: :products_count
belongs_to :product
end
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