rails activerecord：如何指定与“belongs_to ...：class_name ...”的反比关系

Question

我有belongs_to ... :class_name关联工作正常，但无法看到如何创建相互关联。

这是我现在有：

class Contact < ActiveRecord::Base 
    # has fields email_id and phone_id 
    belongs_to :email, :class_name => 'Rolodex' # this works fine 
    belongs_to :phone, :class_name => 'Rolodex' # this works fine 
end 

class Rolodex < ActiveRecord::Base 
    # entry:string holds a phone#, email address, etc 
    has_many :contacts # does NOT WORK, since no Contact.rolodex_id field 
end 

人和协会在联系工作正常 - >关系网方向（通过名称：电话：电子邮件）

john = Contact.first 
john.phone.entry 
# correctly returns the person's rolodex.entry for their phone, if any 
john.email.entry 
# correctly returns the person's rolodex.entry for their email, if any 

但是，如果我想查找共享rolodex条目我不能使用的所有联系人：

r = Rolodex.first 
r.contacts 
# column contacts.rolodex_id does not exist 

当然，我可以byp S上的关联，并直接进行查找：

Contacts.where("(email_id = ?) OR (phone_id = ?)", r.id. r.id) 

但我相信有一些（更好）的方式，例如，指定belongs_to ... :class_name协会的倒数的方式吗？

Answer 1

像下面的内容将工作：

class Rolodex < ActiveRecord::Base 
    has_many :email_contacts, class_name: 'Contact', foreign_key: 'email_id' 
    has_many :phone_contacts, class_name: 'Contact', foreign_key: 'phone_id' 

    def contacts 
    email_contacts + phone_contacts 
    end 
end