多态关联Rails中 [英] Polymorphic Associations in Rails

问题描述

如何多态协会Rails的工作？他们有什么优势？有没有办法只是通过运行迁移添加 belongs_to的方法？

How do polymorphic associations work in Rails? What are their advantages? Is there a way to add belongs_to method just by running a migration?

推荐答案

瑞安有一个 railscast 这个是pretty不错。

Ryan has a railscast about this that is pretty good.

belongs_to的是不是你添加到迁移的东西，你把它添加到模型中。在迁移，您必须添加外键列。例如，如果你有一个属于用户的模式后，你会user_id列增加到帖子中的ActiveRecord迁移。然后添加

Belongs_to isn't something you add to a migration, you add it to the model. In the migration, you have to add the foreign key column. For example if you have a post model that belongs to a user, you'd add the user_id column to the post activerecord in a migration. Then you add

 belongs_to :user

在后单独的模型。那么Rails会做它的魔力在后台给你的用户模型代理集合。

in the post model separately. Then rails will do its magic in the background to give you the proxy collections in the user model.

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