如何通过关联在 has_many 上指定连接表？

Question

这是我的表上的架构信息：

• table_name：admin_users，primary_key：id
• table_name：UserCompanies，primary_key：UserCompanyId，foreign_keys：[CompanyId, UserId]
• table_name：Companies，primary_key：CompanyId'

我想做如下的事情：

AdminUser.first.companies

但是，到目前为止，我的尝试都不起作用，我假设是因为我需要指定表名、模型名或键名，但我不知道它如何与 has_many through 关系一起工作。这是我迄今为止定义它的最佳尝试：

class AdminUser < ActiveRecord::Base
    has_many :user_companies, class_name:"TableModule::UserCompany", foreign_key:"UserId"
    has_many :companies, through: :user_companies, class_name: "TableModule::Company"
end

# this code is from a rails engine separate from the app where AdminUser is defined
# the purpose of the engine is to provide access to this particular database 
# the CustomDBConventions class adapts the models for this database to work with ActiveRecord so we can use snake case attributes, reference the primary key as 'id', and it specifies the correct tables names.
module TableModule
    class UserCompany < CustomDBConventions
        belongs_to :admin_user
        belongs_to :company
    end

    class Company < CustomDBConventions
        has_many :admin_users, through: :user_companies
    end

    class CustomDBConventions < ActiveRecord::Base
        self.abstract_class = true
        def self.inherited(subclass)
            super
            subclass.establish_connection "table_module_#{Rails.env}".to_sym
            tb_name = subclass.table_name.to_s.gsub(/^table_module_/,"").classify.pluralize
            subclass.table_name = tb_name
            subclass.primary_key = tb_name.singularize + "Id"
            subclass.alias_attribute :id, subclass.primary_key.to_sym
            subclass.column_names.each do |pascal_name|
                subclass.alias_attribute pascal_name.underscore.to_sym, pascal_name.to_sym
                subclass.alias_attribute "#{pascal_name.underscore}=".to_sym, "#{pascal_name}=".to_sym
            end
        end
    end
end

编辑：所以这个设置非常接近，我只缺少 1 个外键规范。当我运行 AdminUser.first.companies 时出现 sql 错误：

TinyTds::Error: Invalid column name 'company_id'.: EXEC sp_executesql N'SELECT [Companies].* FROM [Companies] INNER JOIN [UserCompanies] ON [Companies].[CompanyId] = [UserCompanies].[company_id ] WHERE [UserCompanies].[UserId] = @0', N'@0 int', @0 = 1

所以我只需要指定在此加入上使用 UserCompanies.CompanyId。如何正确指定此外键？

Answer 1

假设 TableModule::UserCompany 模型具有这些关联...

class TableModule::UserCompany < ActiveRecord::Base
  belongs_to :admin_user
  belongs_to :company
end

...那么我认为这就是你所追求的：

class AdminUser < ActiveRecord::Base
  has_many :companies, through: :user_company, class_name: "TableModule::UserCompany"
end

Answer 2

我不确定你在用 TableModule 前缀做什么，但以下应该可以工作：

class AdminUser < ActiveRecord::Base
  has_many :user_companies
  has_many :companies, through: :user_companies
end

class Company < ActiveRecord::Base
  has_many :user_companies
  has_many :admin_users, through: :user_companies
end

class UserCompany < ActiveRecord::Base
  belongs_to :admin_user
  belongs_to :comany
end