Ar多重连接

Question

我有以下几种型号：

class Distributor < ActiveRecord::Base
  has_many :products
end

class Producer < ActiveRecord::Base
   has_many :products
end

class Product < ActiveRecord::Base
  has_one :favorite
  belongs_to :producer
  belongs_to :distributor
end

class Favorite < ActiveRecord::Base
  belongs_to :product
end

class User < ActiveRecord::Base
  has_many :favorites
end

我想构建一个AR表达式，它类似于sql查询：

select *
from `favorites`
inner join `products` on `products`.`id` = `favorites`.`product_id`
inner join `producers` on `producers`.`id` = `products`.`producer_id`
inner join `distributors` on `distributors`.`id` = `products`.`distributor_id`
where `favorites`.`user_id` = 1

Answer 1

您可以使用一组嵌套的joins方法，如下所示：

Favorite.joins(:product => [:producer , :distributor]).where("favorites.user_id = 1")

请注意，我使用的是=>表示法，但您也可以使用ruby 1.9+ 1。