ActiveRecord destroy方法 - 参数个数错误(0表示1)

Question

我有3个桌子和3个模型:

Car.rb

  has_many :cars_domains, :dependent => :delete_all
  has_many :domains, :through => :cars_domains

Domain.rb

has_many :cars_domains
has_many :cars, :through => :cars_domains

和cars_domain.rb

class CarsDomain < ActiveRecord::Base
  belongs_to :car
  belongs_to :domain

  attr_accessible :car_id, :domain_id
end

class CreateCarsDomains < ActiveRecord::Migration
  def change
    create_table :cars_domains, :id => false do |t|
      t.references :car, :domain
      t.timestamps
    end

    add_index :cars_domains, [:car_id, :domain_id]
  end
end

一辆汽车可以在某些领域.当我创建一辆汽车并绑定一个域名时,一切都很顺利.

但是当我尝试从cars_domains表中删除时,我有错误:

CarsDomain.where(:car_id => 2, :domain_id => 1).destroy
ArgumentError: wrong number of arguments (0 for 1)

要么

 CarsDomain.where(:car_id => 2, :domain_id => 1).destroy_all

  CarsDomain Load (0.5ms)  SELECT "cars_domains".* FROM "cars_domains" WHERE "cars_domains"."car_id" = 2 AND "cars_do
mains"."domain_id" = 1

   (0.2ms)  SAVEPOINT active_record_1
Could not log "sql.active_record" event. NoMethodError: undefined method `name' for nil:NilClass
   (0.3ms)  ROLLBACK TO SAVEPOINT active_record_1
ActiveRecord::StatementInvalid: PGError: ERROR:  zero-length delimited identifier at or near """"
LINE 1: DELETE FROM "cars_domains" WHERE "cars_domains"."" = $1
                                                        ^
: DELETE FROM "cars_domains" WHERE "cars_domains"."" = $1
        from /usr/local/lib/ruby/gems/1.9.1/gems/activerecord-3.1.3/lib/active_record/connection_adapters/postgresql_
adapter.rb:1062:in `prepare'

怎么了？

UPD:

CarsDomain.destroy_all(:car_id => 2, :domain_id => 1)

CarsDomain负荷(0.9ms)SELECT "cars_domains".*FROM "cars_domains" WHERE "cars_domains". "car_id"= 2且 "cars_do电源". "域ID"= 1(在0.2ms)SAVEPOINT active_record_1无法登录"sql.active_record "事件.NoMethodError:未定义的方法`名"的零:NilClass(为0.2ms)ROLLBACK TO SAVEPOINT active_record_1的ActiveRecord :: StatementInvalid:PGError:错误:零长度分隔标识符处或附近 "" "" LINE 1:DELETE FROM "cars_domains" WHERE" cars_domains".""= $ 1 ^:DELETE FROM"cars_domains"WHERE"cars_domains".""= $ 1

UPD 2

我认为ID中的问题---- create_table:cars_domains,:id => false.因为Destroy方法需要它.

Answer 1

因为你有更多的条目,它属于CarsDomain.CarsDomain#destroy需要一个id,这就是你得到这条消息的原因.使用destory_all条件!

CarsDomain.destroy_all(:car_id => 2, :domain_id => 1)