mysql - after_update 回调不会更新属性

Question

美好的一天...我已经为将要更新的特定列实现了 after_update 回调，并且在更新该列之后，回调意味着将新更新的值添加到另一列，即

class Product < ActiveRecord::Base
after_update :update_stock, :if => :produced_changed?

private 

def update_stock
    self.stock = self.stock + self.produced 
end     
end

当我运行 Rails 控制台并运行“Product.update produced:450”时，stock 列将自动添加新值。即它工作得很好但是当我尝试从“ View / Controller ”更新时它根本不起作用。

请问有什么原因吗？

2.2.4 :004 > h
 => Product id: 1, name: "MAC Air Filter", partnumber: 33440, description: "Air filter", **stock: 3440**, created_at: "2016-04-08 11:38:58", updated_at: "2016-04-19 20:33:00", **produced: 33** 

2.2.4 :006 > h.update **produced:3000**
   (0.1ms)  SAVEPOINT active_record_1
  SQL (1.4ms)  UPDATE "products" SET "produced" = ?, "updated_at" = ? WHERE "products"."id" = ?  [[**"produced", 3000**], ["updated_at", "2016-04-20 13:57:59.377954"], ["id", 1]]
   (0.1ms)  RELEASE SAVEPOINT active_record_1
 => true 

2.2.4 :007 > h
 => Product id: 1, name: "MAC Air Filter", partnumber: 33440, description: "Air filter", **stock: 6440**, created_at: "2016-04-08 11:38:58", updated_at: "2016-04-20 13:57:59", **produced: 3000**> 

Answer 1

您已保存产品库存以更新 产品。在 update_stock 回调中，您只设置产品库存的值。 self.stock = self.stock + self.produced 只设置产品库存的值。

要更新股票值(value)，您必须在回调中保存为:

class Product < ActiveRecord::Base
after_update :update_stock, :if => :produced_changed?

private 

def update_stock
    self.stock = self.stock + self.produced
    self.save
end     
end

但它运行无限循环并给出错误。所以你必须在更新之前使用 before_update 回调设置股票值(value)。

  class Product < ActiveRecord::Base
    before_update :update_stock, :if => :produced_changed?

    private 

    def update_stock
        self.stock = self.stock + self.produced
    end     
 end

并且在 Controller 中保存产品的值(value)。