Solution:Step 1: Understand extend behaviorUsing extend Tracker adds Tracker's methods as class methods to MyClass.Step 2: Check where method_added is definedmethod_added is defined on Tracker's singleton class, not on MyClass's singleton class, so it is not triggered for MyClass instance methods.Fi

[Solved] Consider this code:module Tracker def self.method_added(name) puts "Tracked:... end end Why does method_added not print anything when test is defined? | Ruby

Ruby - Advanced Metaprogramming

Consider this code:

module Tracker
  def self.method_added(name)
    puts "Tracked: #{name}"
  end
end

class MyClass
  extend Tracker

  def test; end
end

Why does method_added not print anything when test is defined?

ABecause method_added must be defined as instance method

BBecause extend does not add instance methods

CBecause method_added is defined on the module's singleton class, not MyClass's singleton class

DBecause test is a class method, not instance method

Step-by-Step Solution

Solution:

Step 1: Understand extend behavior
Using extend Tracker adds Tracker's methods as class methods to MyClass.
Step 2: Check where method_added is defined
method_added is defined on Tracker's singleton class, not on MyClass's singleton class, so it is not triggered for MyClass instance methods.
Final Answer:
Because method_added is defined on the module's singleton class, not MyClass's singleton class -> Option C
Quick Check:
method_added must be on class singleton to catch instance methods [OK]

Quick Trick: method_added triggers only on class singleton, not module singleton [OK]

Common Mistakes:

Assuming extend adds instance methods
Confusing class and instance methods
Expecting method_added to work from module singleton

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Consider this code:

Step 1: Understand extend behavior

Step 2: Check where method_added is defined

Final Answer:

Quick Check:

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