[Solved] You are designing a payment processing system that must support new payment methods without changing existing code. Which design approach best aligns with the Open/Closed Principle? | OOP & Design Patterns

OOP & Design Patterns - Open/Closed Principle - Open for Extension, Closed for Modification

You are designing a payment processing system that must support new payment methods without changing existing code. Which design approach best aligns with the Open/Closed Principle?

ACreating a new subclass for each payment method that implements a common payment interface

BModifying the existing payment processor class to handle new payment methods directly

CAdding new conditional branches inside the existing payment processor class for each new payment method

DUsing global variables to switch between payment methods at runtime

Step-by-Step Solution

Step 1: Identify extension vs modification
Adding new payment methods should extend behavior without modifying existing classes.
Step 2: Evaluate subclassing with common interface
Creating subclasses for each payment method allows extension by adding new classes, adhering to OCP.
Step 3: Why other options fail
Adding new conditional branches inside the existing payment processor class for each new payment method and modifying existing code violate the 'closed for modification' part. Using global variables to switch between payment methods at runtime uses global state, which is unrelated and error-prone.
Final Answer:
Option A -> Option A
Quick Check:
Extension via polymorphism, no modification of existing code.

Quick Trick: Extend with new classes, don't modify existing ones [OK]

Common Mistakes:

MISTAKES

Thinking adding conditionals is extension
Believing modifying existing code is acceptable if tested
Confusing global state management with OCP

Trap Explanation:

PITFALL

Options A and B seem straightforward but violate the principle by modifying existing code; option D distracts with unrelated global state usage.

Interviewer Note:

CONTEXT

Tests candidate's ability to recognize when and how to apply OCP in design.

Master "Open/Closed Principle - Open for Extension, Closed for Modification" in OOP & Design Patterns

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Solution Trace

More OOP & Design Patterns Quizzes

You are designing a payment processing system that must support new payment methods without changing existing code. Which design approach best aligns with the Open/Closed Principle?

Step 1: Identify extension vs modification

Step 2: Evaluate subclassing with common interface

Step 3: Why other options fail

Final Answer:

Quick Check:

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