You want to create a Ruby class Counter that keeps track of how many times its class method increment is called. Which code correctly implements this behavior?
hard📝 Application Q15 of 15
Ruby - Class Methods and Variables
You want to create a Ruby class Counter that keeps track of how many times its class method increment is called. Which code correctly implements this behavior?
Aclass Counter
def self.increment
@count ||= 0
@count += 1
end
def self.count
@count
end
end
Bclass Counter
@count = 0
def increment
@count += 1
end
def count
@count
end
end
Cclass Counter
def self.increment
@@count += 1
end
def self.count
@@count
end
end
Dclass Counter
def increment
@@count ||= 0
@@count += 1
end
def count
@@count
end
end
Step-by-Step Solution
Solution:
Step 1: Understand class variable vs class instance variable
Using @@count is a class variable shared across subclasses, but @count inside class methods is a class instance variable, safer for this use.
Step 2: Check method definitions
class Counter
def self.increment
@count ||= 0
@count += 1
end
def self.count
@count
end
end uses @count ||= 0 inside the class method to initialize the class instance variable, then increments it. It also provides a class method count to read the value.
Final Answer:
class Counter
def self.increment
@count ||= 0
@count += 1
end
def self.count
@count
end
end -> Option A
Quick Check:
Use class instance variable @count inside self methods [OK]
Quick Trick:Use @count with ||= inside self methods to track class state [OK]
Common Mistakes:
Using instance methods to change class state
Using @@count without initialization causing errors
Confusing instance variables with class variables
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