ruby-on-rails - Rails 交易 : save data in multiple models

Question

我的模特

class Auction
  belongs_to :item
  belongs_to :user, :foreign_key => :current_winner_id
  has_many :auction_bids

end

class User
  has_many :auction_bids

end

class AuctionBid
  belongs_to :auction
  belongs_to :user

end

当前使用情况

页面上显示拍卖，用户输入金额并点击出价。 Controller 代码可能如下所示:

class MyController
  def bid
    @ab = AuctionBid.new(params[:auction_bid])
    @ab.user = current_user
    if @ab.save
      render :json => {:response => 'YAY!'}
    else
      render :json => {:response => 'FAIL!'}
    end
  end 
end

所需的功能

到目前为止，这很好用!但是，我需要确保发生其他一些事情。

@ab.auction.bid_count需要加一。

@ab.user.bid_count需要加一

@ab.auction.current_winner_id需要设置为 @ab.user_id

也就是说， User和 Auction与 AuctionBid 相关联还需要更新值以用于 AuctionBid#save返回真。

Answer 1

保存和销毁自动包装在一个事务中
ActiveRecord::Transactions::ClassMethods

Both Base#save and Base#destroy come wrapped in a transaction that ensures that whatever you do in validations or callbacks will happen under the protected cover of a transaction. So you can use validations to check for values that the transaction depends on or you can raise exceptions in the callbacks to rollback, including after_* callbacks.

真正的大会!

class AuctionBid < ActiveRecord::Base
  
  belongs_to :auction, :counter_cache => true
  belongs_to :user
  
  validate              :auction_bidable?
  validate              :user_can_bid?
  validates_presence_of :auction_id
  validates_presence_of :user_id

  # the real magic!
  after_save  :update_auction, :update_user
  
  def auction_bidable?
    errors.add_to_base("You cannot bid on this auction!") unless auction.bidable?
  end
  
  def user_can_bid?
    errors.add_to_base("You cannot bid on this auction!") unless user.can_bid?
  end
  
  protected
  
  def update_auction
    auction.place_bid(user)
    auction.save!
  end
  
  def update_user
    user.place_bid
    user.save!
  end
  
end

荣誉奖
弗朗索瓦·博索莱 +1。感谢您的 :foreign_key推荐，但 current_winner_*列需要缓存在数据库中以优化查询。
亚历克斯 +1。感谢您让我开始使用 Model.transaction { ... } .虽然这最终对我来说并不是一个完整的解决方案，但它确实帮助我指明了正确的方向。