[Solved] You are designing a system for different types of vehicles where... Which design approach best supports adding new capabilities like flying or floating without modifying existing vehicle classes? | OOP & Design Patterns

OOP & Design Patterns - Composition vs Inheritance - Favour Composition, Why & When

You are designing a system for different types of vehicles where some can fly and some can float on water. Which design approach best supports adding new capabilities like flying or floating without modifying existing vehicle classes?

AUse inheritance to create subclasses like FlyingCar and FloatingCar from Vehicle

BUse a single Vehicle class with flags indicating if it can fly or float

CUse composition by creating separate capability classes like FlyBehavior and FloatBehavior and compose them with Vehicle

DUse inheritance and override methods in each subclass to add flying or floating behavior

Step-by-Step Solution

Step 1: Identify the problem with inheritance here
Inheritance leads to a combinatorial explosion of subclasses (FlyingCar, FloatingCar, FlyingFloatingCar), making the design rigid and hard to maintain.
Step 2: Understand composition benefits
Composition allows attaching behaviors dynamically via separate classes (FlyBehavior, FloatBehavior), promoting flexibility and easier extension.
Step 3: Analyze other options
Options A and C rely on inheritance, causing tight coupling and poor scalability. Use a single Vehicle class with flags indicating if it can fly or float uses flags, which leads to complex conditional logic and violates single responsibility.
Final Answer:
Option C -> Option C
Quick Check:
Composition supports adding new capabilities without modifying existing classes, enhancing maintainability and flexibility.

Quick Trick: Composition lets you add capabilities by combining behaviors, inheritance forces rigid hierarchies.

Common Mistakes:

MISTAKES

Assuming inheritance is always better for code reuse
Using flags instead of behaviors leads to messy conditionals

Trap Explanation:

PITFALL

Inheritance seems simpler but leads to rigid, brittle designs when behaviors multiply; flags seem easy but cause complex conditional logic.

Interviewer Note:

CONTEXT

Tests candidate's ability to recognize when composition is preferable over inheritance for flexible design.

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More OOP & Design Patterns Quizzes

Which design approach best supports adding new capabilities like flying or floating without modifying existing vehicle classes?

Step 1: Identify the problem with inheritance here

Step 2: Understand composition benefits

Step 3: Analyze other options

Final Answer:

Quick Check:

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