Given the following Python code using the Decorator Pattern, what is the output of print(coffee.description()) and print(coffee.cost()) after wrapping a SimpleCoffee with MilkDecorator (amount=2) and then SugarDecorator (amount=1)?

easy🧾 Code Trace Q12 of Q15

OOP & Design Patterns - Decorator Pattern - Wrapping Behaviour Without Subclassing

Given the following Python code using the Decorator Pattern, what is the output of print(coffee.description()) and print(coffee.cost()) after wrapping a SimpleCoffee with MilkDecorator (amount=2) and then SugarDecorator (amount=1)?

ACoffee, Milk(2), Sugar(1) 6.3

BCoffee, Sugar(1), Milk(2) 5.8

CCoffee, Sugar(1), Milk(2) 6.3

DCoffee, Milk(2), Sugar(1) 5.8

Step-by-Step Solution

Step 1: Trace description calls
Starting from SugarDecorator: description() calls MilkDecorator.description(), which calls SimpleCoffee.description() returning "Coffee". Then MilkDecorator adds ", Milk(2)", SugarDecorator adds ", Sugar(1)" -> "Coffee, Milk(2), Sugar(1)".
Step 2: Trace cost calls
SimpleCoffee.cost() = 5. MilkDecorator adds 0.5 * 2 = 1. SugarDecorator adds 0.3 * 1 = 0.3. Total cost = 5 + 1 + 0.3 = 6.3.
Final Answer:
Option A -> Option A
Quick Check:
Description order matches wrapping order; cost sums correctly [OK]

Quick Trick: Decorator calls chain in wrapping order [OK]

Common Mistakes:

MISTAKES

Mixing order of decorators in description
Forgetting to multiply cost by amount

Trap Explanation:

PITFALL

Candidates often confuse the order of decorator calls or forget to accumulate costs properly.

Interviewer Note:

CONTEXT

Tests ability to mentally execute decorator chaining and accumulation.

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Given the following Python code using the Decorator Pattern, what is the output of print(coffee.description()) and print(coffee.cost()) after wrapping a SimpleCoffee with MilkDecorator (amount=2) and then SugarDecorator (amount=1)?

Step 1: Trace description calls

Step 2: Trace cost calls

Final Answer:

Quick Check:

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