Included hook in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a module with an included hook method.

Ruby

module Greetings
  def self.[1](base)
    puts "Module included in #{base}"
  end
end

Drag options to blanks, or click blank then click option'

Aincluded

Bextend

Cinclude

Dinitialize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'include' instead of 'included' for the hook method.

Defining the hook as an instance method instead of a class method.

The included method is a special hook in Ruby modules that runs when the module is included in another class or module.

2fill in blank

medium

Complete the code to include the module and trigger the included hook.

Ruby

class Person
  [1] Greetings
end

Drag options to blanks, or click blank then click option'

Aextend

Binclude

Cprepend

Dusing

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'extend' which adds methods as class methods instead of instance methods.

Using 'prepend' which changes method lookup order.

The include keyword adds the module's methods as instance methods to the class and triggers the included hook.

3fill in blank

hard

Fix the error in the included hook method definition.

Ruby

module Logger
  def self.included(base)
    base.[1] LoggerMethods
  end
end

Drag options to blanks, or click blank then click option'

Ainclude

Busing

Cextend

Dprepend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'include' instead of 'extend' inside the included hook.

Not calling any method on base, causing no effect.

Inside the included hook, calling base.extend LoggerMethods adds methods as class methods to the including class.

4fill in blank

hard

Fill both blanks to define a module with an included hook that adds class methods.

Ruby

module Trackable
  def self.[1](base)
    base.[2] ClassMethods
  end

  module ClassMethods
    def track
      puts "Tracking enabled"
    end
  end
end

Drag options to blanks, or click blank then click option'

Aincluded

Binclude

Cextend

Dprepend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'include' instead of 'extend' to add class methods.

Misnaming the hook method.

The included hook is used to call extend on the base class to add class methods from the nested module.

5fill in blank

hard

Fill all three blanks to create a module with an included hook that adds instance and class methods.

Ruby

module Auditable
  def self.[1](base)
    base.[2] InstanceMethods
    base.[3] ClassMethods
  end

  module InstanceMethods
    def audit
      puts "Instance audit"
    end
  end

  module ClassMethods
    def audit
      puts "Class audit"
    end
  end
end

Drag options to blanks, or click blank then click option'

Aincluded

Binclude

Cextend

Dprepend

Attempts:

3 left

💡 Hint

Common Mistakes

Using extend for instance methods or include for class methods.

Forgetting to define the hook as a class method.

The included hook calls include to add instance methods and extend to add class methods to the base.

Practice

1.

What does the included hook do in a Ruby module?

easy

A. It runs only when the module is extended, not included.

B. It runs code automatically when the module is included in a class.

C. It prevents the module from being included in any class.

D. It defines a method that must be called manually.

Solution

1. Step 1: Understand the purpose of the included hook

   The included hook is a special method in Ruby modules that runs automatically when the module is included in a class.

2. Step 2: Compare options with the definition

   Only It runs code automatically when the module is included in a class. correctly describes this automatic behavior. Other options describe manual calls, prevention, or extension, which are incorrect.

3. Final Answer:

   It runs code automatically when the module is included in a class. -> Option B

4. Quick Check:

   Included hook = automatic run on include [OK]

Hint: Remember: included runs automatically on module inclusion [OK]

Common Mistakes:

• Thinking included runs on extend instead of include
• Believing included requires manual method calls
• Confusing included with preventing inclusion

2.

Which of the following is the correct syntax to define an included hook inside a Ruby module?

module Example
  # What goes here?
end

easy

A. def self.included(base)
puts "Included in #{base}"
end

B. def included(base)
puts "Included in #{base}"
end

C. def included
puts "Included"
end

D. def self.include(base)
puts "Included in #{base}"
end

Solution

1. Step 1: Recall how to define class methods in modules

   The included hook must be a module method, so it needs to be defined with self.included.

2. Step 2: Check the method signature

   The method receives the including class as a parameter, so it must accept one argument (base).

3. Final Answer:

   def self.included(base) puts "Included in #{base}" end -> Option A

4. Quick Check:

   included hook = def self.included(base) [OK]

Hint: Use def self.included(base) for included hook syntax [OK]

Common Mistakes:

• Defining included without self (instance method instead of module method)
• Missing the base parameter
• Using def self.include instead of included

3.

What will be the output of this Ruby code?

module Greetings
  def self.included(base)
    puts "Greetings included in #{base}"
  end
end

class Person
  include Greetings
end

medium

A. SyntaxError

B. No output

C. Greetings included in Person

D. Greetings included in Greetings

Solution

1. Step 1: Identify when included hook runs

   The included hook runs automatically when the module is included in a class.

2. Step 2: Check the output inside the included method

   The method prints "Greetings included in #{base}", where base is the class Person.

3. Final Answer:

   Greetings included in Person -> Option C

4. Quick Check:

   included hook prints class name on include [OK]

Hint: included hook prints message with class name on include [OK]

Common Mistakes:

• Expecting no output because included is a hook
• Confusing base with module name
• Thinking included runs on class definition, not include

4.

Find the error in this Ruby code using the included hook:

module Logger
  def included(base)
    base.extend(ClassMethods)
  end

  module ClassMethods
    def log(msg)
      puts "Log: #{msg}"
    end
  end
end

class App
  include Logger
end

App.log("Start")

medium

A. The include statement should be extend.

B. The ClassMethods module should be included, not extended.

C. The log method should be an instance method, not class method.

D. The included method should be defined as self.included, not instance method.

Solution

1. Step 1: Check how included hook is defined

   The included hook must be a module method, defined as self.included, not an instance method.

2. Step 2: Understand the effect of incorrect definition

   Defining included without self means it won't run automatically on include, so base.extend won't happen.

3. Final Answer:

   The included method should be defined as self.included, not instance method. -> Option D

4. Quick Check:

   included hook must be self.included [OK]

Hint: Define included as self.included to run on module include [OK]

Common Mistakes:

• Defining included without self
• Confusing extend and include in hook
• Trying to call class method on instance

5.

You want to add a class method greet to any class that includes your module Friendly. Which is the best way to do this using the included hook?

module Friendly
  # Fill in the included hook
end

class Dog
  include Friendly
end

puts Dog.greet

hard

A. Define self.included(base) and inside it call base.extend with a module containing greet.

B. Define an instance method greet inside Friendly module.

C. Define a class method greet directly inside Friendly module without included hook.

D. Call include Friendly inside Dog.greet method.

Solution

1. Step 1: Understand how to add class methods via included hook

   To add class methods, define self.included(base) and call base.extend with a module containing those methods.

2. Step 2: Why other options fail

   Instance methods won't be class methods; defining class methods directly in module won't add them to including class; calling include inside method is incorrect.

3. Final Answer:

   Define self.included(base) and inside it call base.extend with a module containing greet. -> Option A

4. Quick Check:

   Use included hook + base.extend for class methods [OK]

Hint: Use included hook with base.extend to add class methods [OK]

Common Mistakes:

• Defining greet as instance method instead of class method
• Not using included hook to extend class
• Trying to call include inside a method