氩多个连接

Question

我有以下型号：

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 

我想建立一个AR表达是SQL查询的模拟：

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，如这样的：

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

请注意，我现在用的是=>符号，但是你可以使用红宝石1 .9+也是。