LLD - Design — Online Shopping Cart
You need to add a new payment method 'CryptoPayment' to an existing system using the Payment Strategy Pattern. What is the best approach?
You need to add a new payment method 'CryptoPayment' to an existing system using the Payment Strategy Pattern. What is the best approach?
hard📝 Trade-off Q8 of 15
Step-by-Step Solution
Solution:
Step 1: Follow open-closed principle
Adding new payment methods should not modify existing code but extend it.Step 2: Implement new strategy class
Create CryptoPayment class implementing PaymentStrategy interface and use it in context without changing existing classes.Final Answer:
Create a new class implementing the PaymentStrategy interface and add it to the context -> Option AQuick Check:
Extend by new class, don't modify existing code [OK]
Quick Trick: Add new strategy class to extend payment methods [OK]
Common Mistakes:
- Modifying existing classes breaking open-closed principle
- Adding methods to context for each payment type
- Replacing interface causing backward incompatibility
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