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我在 2 个 mongoid 模型之间有 1 对 1 的关联，并且我不断得到重复，即有多个具有相同 parent_id（即用户）的子记录（卡）。我已尝试验证如下所示的 belongs_to 关联的唯一性，但它不起作用。

 class User
   include Mongoid::Document
   field :name, type: String 
   has_one :card
 end

第二种型号：

 class Card
   include Mongoid::Document
   field :name, type: String 
   belongs_to :user

   validates :user, :uniqueness => {:scope => :user_has_child}

   def user_has_child
     q = Segment.where(drop_id: {'$ne' =>  nil})
     s = q.map(&:drop_id)
     errors.add(:drop_id, "this user already has a card") if s.include?(:drop_id)
   end

 end
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1 回答 1

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The syntax is more simple. You just want to make sure there are no 2 documents with the same user_id

class Card
  belongs_to :user

  validates_uniqueness_of :user

You need to use scope if you want the uniqueness of a tuple of n fields. For example, if a User can have at most one card per year, you can write

class Card
 field :year
 belongs_to :user  

 validates_uniqueness_of :user, scope: [:year] # A user can have one card per year

Note that validations apply when you save the model ie. you try to persist the changes. Calling .save will return true or false if some validations fail, but the object in memory is always modified! This is so, for example, you can display previous values in the HTML input fields, so the user knew what he wrote and can fix it (otherwise he'd have to re-write all his information in case of a single mistake)

Also, Mongoid by default handles dirty tracking (this is now the doc for v5.0 but it was the same for Mongoid 4). That is to say, you can call .changed? .changes, etc on the object in memory to see what are the changes compared to the object in the DB.

于 2015-08-04T23:22:45.830 回答