使用两个外键作用域

Question

我有以下架构：

我希望为foreign_keys（author_id和editor_id）以及单独的keys（例如author_proposals和editor_proposals）选择调用proposals，我需要选择懒惰或急切地加载它们（例如User.includes(:proposals) 或不使用joins）。

更新：

#I have the scopes which is like this:
class User < ActiveRecord::Base
  has_many :author_proposals, class_name: 'Proposal', foreign_key: :author_id
  has_many :editor_proposals, class_name: 'Proposal', foreign_key: :editor_id
end

class Proposal < ActiveRecord::Base
  belongs_to :author, class_name: 'User', foreign_key: :author_id
  belongs_to :editor, class_name: 'User', foreign_key: :editor_id
end

但我需要一个通用的，它会给我所有的建议（author_proposals 和editor_proposals），它也会急切地加载它们。我应该在has_many 上使用条件吗？

Answer 1

我会这样做：

class User < ActiveRecord::Base
  has_many :authored_proposals, class_name: 'Proposal', foreign_key: :author_id
  has_many :editored_proposals, class_name: 'Proposal', foreign_key: :editor_id

  def proposals
    Proposal.where('author_id = :id OR editor_id = :id', { id: id }).distinct
  end
end

class Proposal < ActiveRecord::Base
  belongs_to :author, class_name: 'User', foreign_key: :author_id
  belongs_to :editor, class_name: 'User', foreign_key: :editor_id

  def users
    User.where(id: [author_id, editor_id].uniq)
  end
end

Answer 2

你可以这样做：

class User < ActiveRecord::Base
  has_many :authored_proposals, class_name: 'Proposal', foreign_key: :author_id
  has_many :editored_proposals, class_name: 'Proposal', foreign_key: :editor_id

  def proposals
    authored_proposals | editored_proposals
  end
end

class Proposal < ActiveRecord::Base
  belongs_to :author, class_name: 'User', foreign_key: :author_id
  belongs_to :editor, class_name: 'User', foreign_key: :editor_id

  def users
    author | editor
  end
end

您可以通过以下方式预先加载proposals：User.includes(:authored_proposals, :editored_proposals)。这不是纯粹的 Rails 方式，但对我来说似乎更干净。

---

---

你也可以这样做：

class User < ActiveRecord::Base
  has_many :authored_proposals, class_name: 'Proposal', foreign_key: :author_id
  has_many :editored_proposals, class_name: 'Proposal', foreign_key: :editor_id

  has_many : proposals, finder_sql: proc { "SELECT * FROM proposals WHERE (proposals.author_id = #{id} or proposals. editor_id = #{id})" }
end

Answer 3

这样设置你的关联：

class User < ActiveRecord::Base
  has_many :author_proposals, :class_name => "Proposal", :foreign_key => "author_id"
  has_many :editor_proposals, :class_name => "Proposal", :foreign_key => "editor_id"
end

class Proposal < ActiveRecord::Base
  belongs_to :author, :class_name => 'User', :foreign_key => "author_id"
  belongs_to :editor, :class_name => 'User', :foreign_key => "editor_id"
end