Namespacing with modules in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested module constant access

What is the output of this Ruby code?

Ruby

module Outer
  module Inner
    VALUE = 42
  end
end

puts Outer::Inner::VALUE

A 42

B nil

C NameError

D Outer::Inner::VALUE

💡 Hint

Think about how constants are accessed inside nested modules.

The constant VALUE is defined inside Inner module which is nested inside Outer. Accessing it with Outer::Inner::VALUE returns 42.

❓ Predict Output

intermediate

Method call with same name in different modules

What will this Ruby code print?

Ruby

module A
  def self.greet
    'Hello from A'
  end
end

module B
  def self.greet
    'Hello from B'
  end
end

puts A.greet
puts B.greet

A

Hello from A
Hello from A

B

Hello from B
Hello from A

C

Hello from A
Hello from B

D NoMethodError

💡 Hint

Each module has its own greet method.

Each module defines its own greet method. Calling A.greet prints 'Hello from A' and B.greet prints 'Hello from B'.

🔧 Debug

advanced

Why does this code raise an error?

This code raises an error. What is the cause?

Ruby

module Outer
  module Inner
    def self.message
      'Hi'
    end
  end
end

puts Inner.message

A TypeError - because Inner is not a module

B NoMethodError: undefined method 'message' - because message is not defined

C SyntaxError - because module nesting is incorrect

D NameError: uninitialized constant Inner - because Inner is not accessible without Outer namespace

💡 Hint

Check how you access nested modules outside their parent.

Inner is defined inside Outer, so you must access it as Outer::Inner. Using Inner alone causes a NameError.

📝 Syntax

advanced

Identify the syntax error in module nesting

Which option contains the correct syntax to define a nested module in Ruby?

A module Outer module Inner end end

B module Outer; module Inner; end; end

C module Outer { module Inner } end

D module Outer: module Inner: end end

💡 Hint

Remember Ruby uses 'module' and 'end' keywords with semicolons allowed.

Option B uses correct Ruby syntax with semicolons to separate statements. Others use invalid syntax like braces or colons.

🚀 Application

expert

How many constants are accessible from Outer module?

Given this code, how many constants can be accessed directly using Outer::CONST_NAME?

Ruby

module Outer
  CONST1 = 1
  module Inner
    CONST2 = 2
  end
  CONST3 = 3
end

A 2

B 3

C 1

D 0

💡 Hint

Only constants defined directly inside Outer are accessible as Outer::CONST_NAME.

CONST1 and CONST3 are defined directly inside Outer and accessible as Outer::CONST1 and Outer::CONST3. CONST2 is inside Inner and must be accessed as Outer::Inner::CONST2.