Why is using a class variable (@@count) a bad idea, and what is a better alternative?
hard📝 Application Q8 of 15
Ruby - Class Methods and Variables
You want to track the number of instances created for a class and all its subclasses separately without interference. Why is using a class variable (@@count) a bad idea, and what is a better alternative?
AClass variables are private to each class; use global variables instead.
BClass variables cannot be incremented; use instance variables instead.
CClass variables reset on subclass creation; use constants instead.
DClass variables are shared across subclasses causing interference; use class instance variables instead.
Step-by-Step Solution
Solution:
Step 1: Understand class variable sharing problem
@@count is shared among class and subclasses, so counts mix and interfere.
Step 2: Identify better alternative
Class instance variables (@count) belong to each class separately, avoiding interference.
Final Answer:
Class variables are shared across subclasses causing interference; use class instance variables instead. -> Option D
Quick Check:
Use class instance vars for separate subclass counts [OK]
Quick Trick:Use @count on class, not @@count, for separate subclass tracking [OK]
Common Mistakes:
Using @@count expecting separate subclass values
Using global variables which pollute namespace
Confusing constants with counters
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