所以这是一个示例类
class Company < ActiveRecord::Base
has_many :investments
has_many :vc_firms, through: :investments, source: :investor, source_type: 'VentureFirm'
has_many :angels, through: :investments, source: :investor, source_type: 'Person'
end
@ company.angels和@ company.vc_firms按预期工作。但是，我如何拥有由两种源类型组成的@ company.investors？这适用于投资表中投资者专栏的所有多态？或者也许是使用范围合并所有source_type的方法？
投资模式如下：
class Investment < ActiveRecord::Base
belongs_to :investor, polymorphic: true
belongs_to :company
validates :funding_series, presence: true #, uniqueness: {scope: :company}
validates :funded_year, presence: true, numericality: true
end
天使通过人物模型联系在一起
class Person < ActiveRecord::Base
has_many :investments, as: :investor
end
相关金融机构模型协会：
class FinancialOrganization < ActiveRecord::Base
has_many :investments, as: :investor
has_many :companies, through: :investments
end
以前的解决方案是错误的，我误解了其中一个关系。
Rails无法为您提供跨越多态关系的has_many方法。原因是实例通过不同的表扩展（因为它们可以属于可能或不在同一个表上的不同模型）。因此，如果您跨越belongs_to多态关系，则必须提供source_type。
话虽如此，假设您可以在投资者中使用继承，如下所示：
class Investor < ActiveRecord::Base
has_many :investments
end
class VcFirm < Investor
end
class Angel < Investor
end
您可以从投资中删除多态选项：
class Investment < ActiveRecord::Base
belongs_to :investor
belongs_to :company
.........
end
并且您将能够跨越关系并将其范围与条件：
class Company < ActiveRecord::Base
has_many :investments
has_many :investors, through :investments
has_many :vc_firms, through: :investments, source: :investor, conditions: => { :investors => { :type => 'VcFirm'} }
has_many :angels, through: :investments, source: :investor, conditions: => { :investors => { :type => 'Angel'} }
end
以前的解决方案是错误的，我误解了其中一个关系。
Rails无法为您提供跨越多态关系的has_many方法。原因是实例通过不同的表扩展（因为它们可以属于可能或不在同一个表上的不同模型）。因此，如果您跨越belongs_to多态关系，则必须提供source_type。
话虽如此，假设您可以在投资者中使用继承，如下所示：
class Investor < ActiveRecord::Base
has_many :investments
end
class VcFirm < Investor
end
class Angel < Investor
end
您可以从投资中删除多态选项：
class Investment < ActiveRecord::Base
belongs_to :investor
belongs_to :company
.........
end
并且您将能够跨越关系并将其范围与条件：
class Company < ActiveRecord::Base
has_many :investments
has_many :investors, through :investments
has_many :vc_firms, through: :investments, source: :investor, conditions: => { :investors => { :type => 'VcFirm'} }
has_many :angels, through: :investments, source: :investor, conditions: => { :investors => { :type => 'Angel'} }
end
我添加了一个方法 Company 通过加入投资表来吸引公司所有投资者的类：
class Company < ActiveRecord::Base
has_many :investments
has_many :vc_firms, :through => :investments, :source => :investor, :source_type => 'VcFirm'
has_many :angels, :through => :investments, :source => :investor, :source_type => 'Angel'
def investors
Investor.joins(:investments).where(:investments => {:company_id => id})
end
end
http://www.brentmc79.com/posts/polymorphic-many-to-many-associations-in-rails 看起来非常有帮助阅读 :source 与 :source_type。
希望能帮助到你！