You want to keep track of how many times a class method call is invoked in class Service. Which code correctly implements this using self. methods and a class instance variable?
hard📝 Application Q8 of 15
Ruby - Class Methods and Variables
You want to keep track of how many times a class method call is invoked in class Service. Which code correctly implements this using self. methods and a class instance variable?
Aclass Service
@calls = 0
def self.call
@calls += 1
end
def self.calls
@calls
end
end
Bclass Service
@@calls = 0
def call
@@calls += 1
end
def calls
@@calls
end
end
Cclass Service
def self.call
calls += 1
end
def self.calls
calls
end
end
Dclass Service
def call
@calls += 1
end
def calls
@calls
end
end
Step-by-Step Solution
Solution:
Step 1: Identify correct use of class instance variable and class methods
class Service
@calls = 0
def self.call
@calls += 1
end
def self.calls
@calls
end
end uses @calls as a class instance variable and increments it inside class method self.call.
Step 2: Check other options for errors
class Service
@@calls = 0
def call
@@calls += 1
end
def calls
@@calls
end
end uses class variables and instance methods incorrectly; Options C and D have syntax or scope errors.
Final Answer:
Option A correctly tracks calls using class instance variable and class methods. -> Option A
Quick Check:
Use class instance vars with self. methods for tracking [OK]
Quick Trick:Use @var with self. methods to track class-level data [OK]
Common Mistakes:
Using instance methods to update class variables
Confusing class variables (@@) with class instance variables (@)
Missing self. prefix for class methods
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