[Solved] Given the following Ruby code:class X @@counter = 0 def initialize @@counter += 1 end def self.counter @@counter end end class Y What will be the output? | Ruby

Ruby - Class Methods and Variables

Given the following Ruby code:

class X
  @@counter = 0
  def initialize
    @@counter += 1
  end
  def self.counter
    @@counter
  end
end

class Y < X; end

X.new
Y.new
Y.new
puts Y.counter

What will be the output?

A3

B2

C1

D0

Step-by-Step Solution

Solution:

Step 1: Understand class variable sharing
Class variables (@@counter) are shared between a class and all its subclasses.
Step 2: Count increments
Each new call increments the shared @@counter by 1. Three instances are created in total.
Step 3: Accessing counter
Calling Y.counter returns the shared @@counter value, which is 3.
Final Answer:
3 -> Option A
Quick Check:
Class variables are shared across subclasses [OK]

Quick Trick: Class variables shared across subclasses count all instances [OK]

Common Mistakes:

Assuming subclasses have separate class variable copies
Expecting Y.counter to return 2 instead of 3
Confusing class variables with instance variables

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More Ruby Quizzes

Given the following Ruby code:

Step 1: Understand class variable sharing

Step 2: Count increments

Step 3: Accessing counter

Final Answer:

Quick Check:

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