E-Commerce – Implementing ‘Buy One Get One Free’ Coupon Logic

design-patternse-commerceobject-orientedPHP

Trying to solve bogo coupon logic with proper design pattern, but having trouble identifying one.
Use case: "Buy iPad get SmartCase for free"

Suppose we have the following objects:

Product:
 - getPrice

CartItem(Product p, quantity):
 - getPrice

Cart:
 - getItems()
 - addItem(CartItem ci)

Coupon(code):
 - getCode

CouponBuyOneGetOneFree(code) extends Coupon: (not sure about inheritance here)

1) What design pattern fits here?
2) What if i needed to set up the same logic without coupon but in product settings itself?

I have implemented Decorator pattern for CartItem when discount is applied to the same CartItem by this example and it works great, but still can not achieve the result of this use case.

Somehow I need to check that Ipad and SmartCase both are in the cart and apply discount to SmartCase only. Also if I add another iPad i should get another SmartCase for free.

Best Answer

No design pattern is required beside basic subclassing. You just need a Coupon interface with a single method: calculateDiscount(cart, customer). Create an implementation of Coupon for each different kind of discount, e.g. a FreeAddonCoupon or a LoyaltyCoupon.

So a Cart has CartItems and Coupons. Add the price of the items, subtract the discount for each coupon.

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E-commerce – Product Search Design in an E-commerce Application

You are optimizing prematurely for facilities that will be extremely costly and which you almost certainly will not need. The only way a new ecommerce system requires the scalability and performance of Amazon's is if you're writing it as a direct replacement for Amazon's existing system. Otherwise, your system will be smaller (probably by multiple orders of magnitude) and run fewer transactions per second (likewise) for the foreseeable future.

Design what you need now, not what you think you may need a year or five down the line. But design it with an abstract interface, so if you need to change it, you can do so without worrying about got other parts of the system interact with ît. That is how you build a scalable system.

More specifically, don't start with a sharded design. Initially, a single database server should be more than adequate. If you find you need to scale it, replication is much simpler than sharding, so should be your first approach. Adding caches at the front end may help, but run them on your front end server... Distributed caches are less performant and unlikely to be necessary.

Java – How to design the classes for a simple shopping cart example using Strategy Design Patterns

Since you are learnig OOP i help you with the busines part:

You have product specific discounts (discount strategy) that depend on cartitem quantity

Milk $0.60
Buy 3 Milk for the price of 2 = discount is 0.60 per 3 Milk = 0.60*int(cartitem.quantity / 3)

cart has 7 milk á 0.60 = 4.20
minus milk-discount int(quanty/3) * 0.60 = int(7/3) * 0.60 = 2 * 0.60 = 1.2


4.20
- 1.2
= 3.00

This should give you enough info to design classes Product , ProductDiscountStrategy, Cart, CartItem

Best Answer

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Java – How to design the classes for a simple shopping cart example using Strategy Design Patterns

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