accepts_nested_attributes_for和validates_uniqueness_of会生成错误的sql请求。

Question

我有奇怪的验证请求。下面是我的代码：

#app/models/user.rb
class User < ActiveRecord::Base
  has_many :exchanges_users, inverse_of: :user
end

#app/models/exchange.rb
class Exchange < ActiveRecord::Base
  has_many :exchanges_users, inverse_of: :exchange
  accepts_nested_attributes_for :exchanges_users, :allow_destroy => true, :reject_if => :all_blank
end

#app/models/exchanges_user.rb
class ExchangesUser < ActiveRecord::Base
  validates_presence_of :exchange
  validates_presence_of :user
  validates_uniqueness_of :exchange, :scope => [:user]

  belongs_to :exchange, inverse_of: :exchanges_users
  belongs_to :user, inverse_of: :exchanges_users
end

并且，在控制台中，当我尝试创建Exchange时：

e = Exchange.new({"name"=>"Test", "exchanges_users_attributes"=>{"0"=>{"user_id"=>"4"}, "1"=>{"user_id"=>"1"}}}) ; e.save

Rails通过这些请求验证了唯一性：

SELECT  1 AS one FROM "exchanges_users" WHERE ("exchanges_users"."exchange_id" IS NULL AND "exchanges_users"."user_id" = 4) LIMIT 1
SELECT  1 AS one FROM "exchanges_users" WHERE ("exchanges_users"."exchange_id" IS NULL AND "exchanges_users"."user_id" = 1) LIMIT 1

显然，"IS NULL“部分是错误的，但我不知道为什么会发生这种情况。你有什么想法吗？

Answer 1

因为您有validates_presence_of :exchange，所以这个查询应该是良性的，但无用。您可以通过首先创建Exchange记录并应用其属性来解决此问题

ActiveRecord::Base.transaction do
  e = Exchange.new
  e.save!(validate: false) 
  e.update_attributes({"name"=>"Test", "exchanges_users_attributes"=>{"0"=>{"user_id"=>"4"}, "1"=>{"user_id"=>"1"}}}) 
  e.save!
end