Ruby on Rails的在多个列的数据库中指定的唯一性 [英] ruby on rails specifying uniqueness in db across multiple columns
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问题描述
我有一个模型,如下:
class EntityTag < ActiveRecord::Base
attr_protected :user_id, :post_id, :entity_id
belongs_to :user
belongs_to :post
belongs_to :entity
validates :user_id, :presence => true
validates :entity_id, :presence => true
validates :post_id, :presence => true
end
我要谨防具有USER_ID,entity_id和的post_id的相同组合多行(例如,某行的唯一ID是所有这三个值)。
I want to guard against multiple rows which have the same combination of user_id, entity_id, and post_id (e.g. a unique ID for a row is all three of those values).
什么是我能传达给ActiveRecord的最简单的方法是什么?
What's the easiest way I can communicate that to ActiveRecord?
推荐答案
由于@dhruvg提到的:
As @dhruvg mentioned:
validates_uniqueness_of :user_id, :scope => [:entity_id, :post_id]
请注意,模型级别的唯一性验证无法保证在数据库中的唯一性。为了有一个,你应该把一个唯一索引在表上。
Do note that uniqueness validation on model level does NOT guarantee uniqueness in the DB. To have that, you should put a unique index on your table.
以下内容添加到您的迁移。
Add the following to your migrations.
add_index :entity_tags, [:user_id, :post_id, :entity_id], :unique => true
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