ruby-on-rails - Rails has_many 通过为多种类型使用 source 和 source_type 别名

Question

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来源类型组成的@company.investors？这对 Investments 表的 Investor 列上的所有多态都有效吗？或者也许是一种使用范围来合并所有 source_type 的方法？

投资模型如下:

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 Person 模型关联

class Person < ActiveRecord::Base
    has_many :investments, as: :investor
end

相关金融组织模型协会:

class FinancialOrganization < ActiveRecord::Base
    has_many :investments, as: :investor
    has_many :companies, through: :investments
end

Answer 1

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。原因是实例分布在不同的表中(因为它们可以属于不同的模型，这些模型可能位于也可能不在同一张表上)。所以，如果你跨越一个belongs_to 多态关系，你必须提供source_type。

话虽如此，假设您可以像这样在 Investor 中使用继承:

class Investor < ActiveRecord::Base
  has_many :investments
end

class VcFirm < Investor
end

class Angel < Investor
end

您将能够从投资中删除多态选项:

class Investment < ActiveRecord::Base
  belongs_to :investor
  belongs_to :company

  .........
end

您将能够跨越关系并根据条件确定其范围:

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