Module declaration syntax in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of module method call

What is the output of this Ruby code?

Ruby

module Greetings
  def self.say_hello
    "Hello from module!"
  end
end

puts Greetings.say_hello

A Hello from module!

B SyntaxError

C NoMethodError

D nil

💡 Hint

Look at how the method is defined with self inside the module.

The method say_hello is defined as a module method using self. Calling Greetings.say_hello prints the string.

❓ Predict Output

intermediate

Output of including a module

What will be printed when this Ruby code runs?

Ruby

module Talk
  def speak
    "I can talk"
  end
end

class Person
  include Talk
end

puts Person.new.speak

A SyntaxError

B NoMethodError

C I can talk

D nil

💡 Hint

Including a module adds its methods as instance methods.

The module Talk is included in Person, so Person instances can call speak, printing 'I can talk'.

❓ Predict Output

advanced

Output of nested module constants

What is the output of this Ruby code?

Ruby

module Outer
  VALUE = 10
  module Inner
    VALUE = 20
    def self.value
      VALUE
    end
  end
end

puts Outer::Inner.value

A nil

B 20

C NameError

D 10

💡 Hint

Constants inside nested modules are accessed by their own scope.

Inner module has its own VALUE constant set to 20. The method returns Inner::VALUE, which is 20.

❓ Predict Output

advanced

Error raised by invalid module syntax

What error does this Ruby code raise?

Ruby

module Sample
  def method
    puts "Hello"
  # missing end here

A SyntaxError

B RuntimeError

C NameError

D NoMethodError

💡 Hint

Check if all blocks and modules are properly closed.

The module and method definitions are not closed with 'end', causing a SyntaxError.

🧠 Conceptual

expert

Number of methods available after module inclusion

Given this Ruby code, how many methods can be called on an instance of class C?

Ruby

module M1
  def a; 1; end
end

module M2
  def b; 2; end
end

class C
  include M1
  include M2
  def c; 3; end
end

obj = C.new

A 0

B 2

C 1

D 3

💡 Hint

Including modules adds their instance methods to the class.

Class C has method c and includes M1 and M2, adding methods a and b. So obj has 3 methods: a, b, c.