shopping cart price change

Question

Say i have a Laptop for 600.00. Say i change it to $650.00. How do shopping carts handle that? Like do they store the price in the cart or the item? How do they make sure they get the price they wanted but not bill the customer the new change without asking them? Or do most store them in both?

I was thinking maybe i could store it in both. So if the current price is over the cart price for a item, don't remove it/bill them from their cart. Then after, tell them what was billed/email a receipt for the items that didn't change that was billed(say they had more then one item) and remove it from the cart. For the items that did change, say something like "Items left in cart due to price change, please check if you still want to buy the items at the new price." So leave the items that changed in the cart but update the price in the cart.

Thats my idea on how to do it. I don't think the language should matter. Guess this is more of a logical type question. Do most shopping carts do it this way or is there a better way?

Answer 1

Simple shopping carts are just arrays of products that are maintained through sessions and cookies. You can do anything you want. Just make sure users can't do anything they want such as change prices through the url. But most of all make it very, very, very easy for the user to checkout.

Most developers will create an array with product objects so if any changes are made to a product shopping carts will reflect this change. However, if you change your prices then obvious you will have a problem if a user clicks on on price but then you change it and the uses doesn't see this change until after they paid or become confused why the price went up mid shopping experience.

In terms of maintaining the line item if you have users sign in before they can add things to a cart then you don't need to worry about creating a cookie/session to store the array of the line items until they do checkout and the line items are saved with their information for later reference.

In this case what you will want to do is create a line item which is associated to the object so you can get all the products information but at the same time store the price in that actual LineItem model so if you do update your price it will not affect shoppers mid buying experience.

And if you want users to pay higher prices because you change your mind and want to use the line item model you can just do what is sated in the last paragraph and check the price right before a user decides to checkout. If it is different then let them no that this product is now x amount to purchase and don't forget to apologize.

Answer 2

The short answer, it all depends on how it was coded.

I assume the transaction that you are talking about is in process. If the price changes after the user completes the transaction, then it would be considered a "Bad Thing" in the terms of customer service, and may potentially be illegal in the eyes of your payments processor.

I like your idea of comparing the price in the cart vs the newest price. However if the user can change the value of the price of an item in the request to view the cart, it could cause many problems with what they actually get charged. For example, if the user changed the price of the laptop to $1200, and in your code you reduced the value in their cart by the difference, they could get that laptop for $0, which would be a "Bad Thing".

$1200 - User Input $600 - Actual Price -$600 - Adjustment against price $0 - price customer is charged?

Another example would be if you make the price of the item a value that the user can edit, and they are a malicious user, they could potentially change the price to -$600.00, which again would be a "Bad Thing".

The more secure way to do it would be to store the item ID of the item in the cart in the link to view the cart, then retrieve/update the price of the item in the cart every time the properties (total, etc) of the cart are requested. That way if a malicious user tried the plus or minus trick, they would just get a message that the price has been updated to the "current price".

The OWASP site has some open source security tools that can help test your code against situations where the user tries to high jack a shopping cart. Their address is http://www.owasp.org

Answer 3

If the cart simply contains a reference to the item (such as the id/primary key), you don't need to store the price in two places at all. You simply load the objects from the cart when you need them, and prices will automatically reflect the change. In most cases, the changes will be infrequent enough that it is not a big deal from a user perspective.