Rails中的交叉唯一性模型验证 [英] Cross uniqueness model validation in rails

问题描述

我有一个模型，希望列包含不同的ID.因此，一个用户可以关注另一个用户，但不能关注自己.

I have a model where I want columns to contain different ids. So a user may follow another user, but not follow themselves.

迁移

class CreateFollows < ActiveRecord::Migration
  def change
    create_table :follows do |t|
      t.integer :follower_id
      t.integer :followee_id

      t.timestamps
    end
  end
end

型号

class Follow < ActiveRecord::Base
  belongs_to :follower, class_name: 'User'
  belongs_to :followee, class_name: 'User'

  validates :follower_id, uniqueness: { scope: :followee_id }
end

但是我的测试似乎失败

测试

it 'cannot follow itself' do
  user = FactoryGirl.create(:user)
  follow = FactoryGirl.create(:follow, follower: user, followee: user)
  expect(follow).to be_invalid
end

输出

Failures:

1) Follow cannot follow itself
 Failure/Error: expect(follow).to be_invalid
   expected `#<Follow id: 27, follower_id: 78, followee_id: 78, created_at: "2014-07-04 02:20:59", updated_at: "2014-07-04 02:20:59">.invalid?` to return true, got false
 # ./spec/models/follow_spec.rb:23:in `block (2 levels) in <top (required)>'

从我读过的所有内容来看，这看起来像是在写.有人有指针吗?

From everything I've read, this looks write. Anyone have any pointers?

谢谢

推荐答案

此验证:

validates :follower_id, uniqueness: { scope: :followee_id }

简单地说，每个followee_id的follower_id集合不能包含重复项(即，您不能跟随一个人两次)，它并没有说明followee_id与follower_id不同.

simply says that the set of follower_ids for each followee_id cannot contain duplicates (i.e. you can't follow one person twice), it says nothing about followee_id being different from follower_id.

如果您想禁止自己跟随自己，则必须这样说:

If you want to disallow following yourself then you have to say so:

  validate :cant_follow_yourself

private

  def cant_follow_yourself
    return if followee_id != follower_id
    # add an appropriate error message here...
  end

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