如何在Ruby on Rails中验证一对ID的唯一性? [英] How do you validate uniqueness of a pair of ids in Ruby on Rails?

问题描述

假设在Ruby中进行以下数据库迁移:

Suppose the following DB migration in Ruby:

    create_table :question_votes do |t|
      t.integer :user_id
      t.integer :question_id
      t.integer :vote

      t.timestamps
    end

进一步假设我希望数据库中的行包含唯一的(user_id，question_id)对.可以在模型中放入合适的粉尘来实现此目的?

Suppose further that I wish the rows in the DB contain unique (user_id, question_id) pairs. What is the right dust to put in the model to accomplish that?

validates_uniqueness_of :user_id, :question_id

似乎只是使行按用户ID唯一，并按问题ID唯一，而不是按行对唯一.

seems to simply make rows unique by user id, and unique by question id, instead of unique by the pair.

推荐答案

validates_uniqueness_of :user_id, :scope => [:question_id]

如果您需要包括另一列(或更多列)，则也可以将其添加到范围中.示例:

if you needed to include another column (or more), you can add that to the scope as well. Example:

validates_uniqueness_of :user_id, :scope => [:question_id, :some_third_column]

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