OOP & Design Patterns - Command Pattern - Undo/Redo, Request Queuing & Logging
Consider the same Command Pattern implementation. What will be the output if you execute a single AddCommand with value 0, then undo it?
Consider the same Command Pattern implementation. What will be the output if you execute a single AddCommand with value 0, then undo it?
medium🧾 Code Trace Q4 of Q15
Step-by-Step Solution
Solution:
Step 1: Execute AddCommand with value 0
Receiver state changes from 0 to 0, prints "Receiver state changed to 0".Step 2: Undo command
Undo reverts 0, state remains 0, prints "Receiver state reverted to 0".Final Answer:
Option D -> Option DQuick Check:
State remains unchanged but output prints both action and revert [OK]
Quick Trick: Undo of zero-value command leaves state unchanged but prints revert [OK]
Common Mistakes:
MISTAKES- Assuming no output for zero-value commands
- Incorrect state changes on zero undo
Trap Explanation:
PITFALL- Candidates often assume zero-value commands produce no output or change state, which is incorrect.
Interviewer Note:
CONTEXT- Tests handling of edge cases with zero-value commands
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