具有嵌套关联条件检查的has_many范围

Question

我有一个具有许多项目的帐户模型，以及一个具有许多要求的项目模型，一个帐户充当库帐户，其他帐户为用户帐户。

需求表具有一个external_id，它是一个字符串ID，用于与外部数据库相关联，并且在帐户的上下文中是唯一的。但是库帐户和用户帐户中的需求可以共享相同的external_id（即“ REQ-23”），因此它不是“需求”表上的唯一键。

有一个RelatedRequirement表，该表映射了相关的需求。

下面，我想通过在has_many范围内进行一个account_id检查来获得属于用户帐户的相关要求。

数据库端：

account
  id

project
  id
  account_id

requirement
  id
  project_id
  external_id

related_requirements
   external_id
   related_external_id

模型侧：

class RelatedRequirement < ActiveRecord::Base
  belongs_to :requirement,,
    foreign_key: :external_id,
    class_name: "Requirement",
    primary_key: :external_id

  belongs_to :related_requirement,
    foreign_key: :related_external_id,
    class_name: "Requirement",
    primary_key: :external_id
end

class Requirement < ActiveRecord::Base
 belongs_to :project
  has_one :account, through: :project

  has_many :related_requirement_mappings,
    foreign_key: :external_id,
    class_name: "RelatedRequirement",
    primary_key: :external_id

  has_many :related_requirements,
    # === this works ===
    #-> { joins(:project).where(projects: {account_id: 2 }) },
    # === this doesn't work ===
    -> { joins(:project).where(projects: {account_id: project.account_id }) },
    through: :related_requirement_mappings, 
    foreign_key: :related_external_id, 
    class_name: "Requirement",
    primary_key: :external_id

我的问题：

主要问题，我希望能够使用上面的has_many：related_requirements在同一个帐户内获取related_requirements，但是我无法进入我范围内的关联account_id，

>req = Requirement.find(1)
>req.related_requirements  

  Requirement Load (81.3ms)  SELECT "requirements".* FROM "requirements"
NameError (undefined local variable or method `project' for #<Requirement::ActiveRecord_Relation:0x00007fe3f0b1ac20>)

但是我目前能做的是：

class Requirement < ActiveRecord::Base

has_many :related_requirements,
    #-> { joins(:project).where(prjects: {account_id: project.account_id }) },
    through: :related_requirement_mappings, 
    foreign_key: :related_external_id, 
    class_name: "Requirement",
    primary_key: :external_id

scope :for_account, -> (account) { joins(:project).where(projects: {account_id: account.id}) }

>req = Requirement.find(1)
>req.related_requirements.for_account(req.account)

这看起来有点愚蠢，因为看起来我在req上调用实例方法，而且我应该能够从related_requirements内部访问req的帐户，而不必定义此额外的for_account范围。

由于external_id不是唯一字段，所以RelatedRequirement表中的belongs_to需求实际上可以映射到多个需求，但只返回一个。理想情况下，我想添加一个范围条件（基于另一个克隆的数据库字段），以表明它来自库帐户。但是，如果我这样做，则上面的related_requirements查询将中断，因为范围条件将包含在查询中，并且不再返回用户帐户的related_requirements，我对此很感兴趣。当我没有明确调用它时，我不确定我在RelatedRequirement范围中指定的条件如何应用于我为需求定义的范围。

class RelatedRequirement < ActiveRecord::Base
  belongs_to :requirement,
    -> { where cloned: nil },
    foreign_key: :external_id,
    class_name: "Requirement",
    primary_key: :external_id

  belongs_to :related_requirement,
    -> { where cloned: nil },
    foreign_key: :related_external_id,
    class_name: "Requirement",
    primary_key: :external_id


class Requirement < ActiveRecord::Base
  belongs_to :project
  has_one :account, through: :project

  has_many :related_requirement_mappings,
    foreign_key: :external_id,
    class_name: "RelatedRequirement",
    primary_key: :external_id

  has_many :related_requirements,
    # -> { joins(:project).where(projects: {account_id: project.account_id }) },
    through: :related_requirement_mappings, 
    foreign_key: :related_external_id, 
    class_name: "Requirement",
    primary_key: :external_id

  scope :for_account, -> (account) { joins(:project).where(projects: {account_id: account.id}) }

irb(main):060:0> r.related_requirements.to_sql
=> "SELECT "requirements".* FROM "requirements" INNER JOIN "related_requirements" ON "requirements"."external_id" = "related_requirements"."related_external_id" WHERE "related_requirements"."external_id" = 'REQ-1' AND "requirements"."cloned" IS NULL"

irb(main):061:0> r.related_requirements.for_account(r.account)
=> #<ActiveRecord::AssociationRelation []>