[Solved] What will be the output of this Ruby code? class Dog def initialize(name) @name = name end end fido = Dog.new('Fido') fido.... end } puts fido.speak rex = Dog.new('Rex') puts rex.respond_to?(:speak) | Ruby

Ruby - Advanced Metaprogramming

What will be the output of this Ruby code?

class Dog
  def initialize(name)
    @name = name
  end
end

fido = Dog.new('Fido')
fido.instance_eval { def speak; "Woof! I'm #{@name}"; end }
puts fido.speak

rex = Dog.new('Rex')
puts rex.respond_to?(:speak)

AWoof! I'm Fido false

BWoof! I'm Fido true

CNoMethodError for fido.speak

DWoof! I'm Fido NoMethodError for rex.speak

Step-by-Step Solution

Solution:

Step 1: Understand instance_eval adds method to one object
The speak method is added only to fido, not to other Dog instances.
Step 2: Check outputs
fido.speak prints "Woof! I'm Fido". rex.respond_to?(:speak) returns false because rex has no speak method.
Final Answer:
Woof! I'm Fido false -> Option A
Quick Check:
instance_eval adds method to one object only [OK]

Quick Trick: instance_eval adds method to one object only [OK]

Common Mistakes:

Assuming all instances get the new method
Expecting true for rex.respond_to?(:speak)
Confusing instance_eval with class_eval

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What will be the output of this Ruby code?

Step 1: Understand instance_eval adds method to one object

Step 2: Check outputs

Final Answer:

Quick Check:

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