RNR：数据库规范化，轨道模型和协会 [英] RnR: Database normalization, rails models and associations

问题描述

好了，我有三个不同的对象：一个人，地点和设备。每个人都可以拥有一个地址，在大多数情况下，多个地址和多个电话号码。所以我的想法是创建特定的对象表中，有一个地址和一个电话表。在这里，我的问题：

Ok, so I have three different objects: a person, place, and equipment. Each can have an address, in most cases multiple address and multiple phone numbers. So my thought is create the specific object tables, the have an address and a phone table. Here my question:

所以通常情况下，在我的SQL的世界，我只想有地址和电话表中的object_id列，并放置在对象ID列中的对象的ID，然后选择所有匹配的地址或电话记录。

So typically, in my SQL world, I would just have an object_id column in the address and phone table and put a id of the object in the object id column, and then select all the address or phone records that match.

我能做到这一点，做的find_by_sql并得到记录，但我宁愿留在ActiveRecord的范式。这是否意味着我应该有一个ID列在表中的每个对象，因此为person_id，place_id等。

I could do this, do find_by_sql and get the records but I'd rather stay within the ActiveRecord paradigm. So does that mean I should have an id column in the table for each object, so a person_id, place_id, etc.

什么是正确的方式来模拟这一点？

What's the "right" way to model this?

推荐答案

您可以创建多态关联与ActiveRecord的，这样你就可以添加的object_id 和对象类型的地址和phone_numbers表，并指定这样的关联：

You can create polymorphic associations with activerecord, so you can add object_id and object_type to the addresses and phone_numbers tables, and specifying the associations like this:

class Address
  belongs_to :object, :polymorphic => true
end

class PhoneNumber
  belongs_to :object, :polymorphic => true
end

class Person
  has_many :addresses, :as => :object
  has_many :phone_numbers, :as => :object
end

class Place
  has_many :addresses, :as => :object
  has_many :phone_numbers, :as => :object
end

class Equipment
  has_many :addresses, :as => :object
  has_many :phone_numbers, :as => :object
end

这样， Person.first.addresses 应运行像查询Addresses.where（：对象类型=＆gt;中人物：OBJECT_ID =＆GT;。Person.first.id），反之为模型和协会的其他

This way, Person.first.addresses should run a query like Addresses.where(:object_type => "Person", :object_id => Person.first.id), and vice versa for the rest of the models and associations.

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