Question

嗨,伙计们,这是我的代码:

class Tailor < ActiveRecord::Base
    has_many    :tailor_items
    has_many    :order_items

    [:collars, :sexes, :sleeves].each do |attribute|
        has_many    attribute, through: :tailor_items, source: :item, source_type: attribute.to_s.classify

    end
 end

class TailorItem < ActiveRecord::Base
  belongs_to        :tailor
  belongs_to        :item, polymorphic: true
end

class Collar < ActiveRecord::Base
end

What I need to do is this: For a given shirt I need to select a tailor. A shirt can have a collar, male/female or a certain type of sleeve. Some tailors can make all collars but only a few sleeves, others can make only male stuff, etc. The priority doesnt matter for this example. The idea is that I end up with 1 tailor.

我试过这个:

tailors = Tailor.joins(:tailor_items).where("(item_id = ? and item_type = ?)",1,"Collar")
if tailors.count > 1
  tailors.where("(item_id = ? and item_type = ?)",2,"Sleeve")
  if tailors.count > 1
     # and so forth.
  end
end

But I never get a row back. If I say:

Tailor.find(1).tailor_items

我得到两个结果(简单的素道代码)

<id: 1, item_type: "Collar"><id:2, item_type:"Sleeve">

第二裁缝:

Tailor.find(2).tailor_items

我得到两个结果(简单的素道代码)

<id: 1, item_type: "Collar"><id:3, item_type:"Sleeve">

but when I try to chain them in the query its no worky... Not even if I put it all in one where:

Tailor.where("(item_id = 1 and item_type =  Collar ) and (item_id = 2 and item_type =  Sleeve )")

我仍然得到0个结果。

Tailor.where("item_id = 1 and item_type =  Collar ") returns: Tailor #1
Tailor.where("item_id = 2 and item_type =  Sleeve ") returns: Tailor #1

他们却一无所获。

Tailor Load (0.0ms) SELECT "tailors".* FROM "tailors" INNER
JOIN "tailor_items" ON "tailor_items"."tailor_id" = "tailors"."id" WHERE ((tailo
r_items.item_id = 1 and tailor_items.item_type =  Collar ) and (tailor_items.ite
m_id = 2 and tailor_items.item_type =  Sleeve ))

我糊涂了...

谢谢你的帮助

I run: Win XP Postgresql Rails 3.2.2

PS: 在多形态组合后完成这个完整的唯一缺少的是 XML 。 : P 否则它只是不够有企业性质而已。

EDIT: Implementing Rob di Marcos scope, I get this SQL:

SELECT "tailors".* FROM "tailors" WHERE 
(EXISTS(SELECT * FROM tailor_items WHERE tailor_items.item_id = 1 and tailor_items.item_type =  Collar )) 
AND (exists(select * from tailor_items where tailor_items.item_id = 2 and tailor_items.item_type =  Sleeve ))

This returns 2 tailors instead of only tailor 1 who can do both (while tailor 2 cant do sleeve #2)

Answer 1

问题是两个行需要匹配的位置。我通常会使用子查询来测试。类似的东西

Tailor.where("exists (select  x  from tailor_items where 
         tailor_id = tailors.id and tailor_items.item_id = ? and 
         tailor_items.item_type=?)", 1,  Collar ).
       where("exists (select  x  from tailor_items where 
         tailor_id = tailors.id and tailor_items.item_id = ? and 
         tailor_items.item_type=?)", 2,  Sleeve )

在这个例子中,我为每个我要找的裁缝物品都有一个小小房间。我可以很容易地把这个范围做成一个关于裁缝的东西,比如:

class Tailor
  # ....
  scope :with_item, lambda{ |item_id, item_type | 
      where("exists (select  x  from tailor_items where 
     tailor_id = tailors.id and tailor_items.item_id = ? and 
     tailor_items.item_type=?)", item_id, item_type)
     }

然后能够将我的定制请求链链起来

Tailor.with_item(1,  Collar ).with_item(2,  Sleeve )

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