Ruby on Rails: Avoiding infinite loop when calling .save during an update

I have an order model that has_many :items. Each item has item.price for the cost of said item. I want to add up all of the item prices in the order for a order.total_price. Right now I'm doing that with

after_save :update_total_price, :if => "self.saved.nil? "


def update_total_price
     self.total_price = Item.find(item_ids).inject(0){|sum,item| sum + (item.price * item.amount) } #amount is how many items there are
     self.saved = 1
     self.save if self.saved
end

This works just fine the first time that I put in the info, but if I try to edit the order, the total_price doesn't get updated because update_total_price doesn't get called because self.saved is not nil.

What can I do to make it so that updating the model will update it, but won't keep on doing an infinite loop 开发者_如何学Pythonof calling .save?

Why not have the update_total_price NOT save the data again.

just set the value in before_update:

before_save :update_total_price

def update_total_price
  self.total_price = items.find(:all).inject(0){|sum,item| sum + (item.price * item.amount) } 
end

after_save :update_total_price

def update_total_price          
   self.total_price = find_total_price
   self.save_without_callbacks
end

def find_total_price
  Item.find(item_ids).inject(0){|sum,item| sum + (item.price * item.amount) 
end