Include for instance methods in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to include the module for instance methods.

Ruby

module Greetings
  def hello
    "Hello!"
  end
end

class Person
  [1] Greetings
end

p = Person.new
puts p.hello

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

Aimport

Bextend

Crequire

Dinclude

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using 'require' or 'import' which are for loading files or libraries.

In Ruby, include adds module methods as instance methods to a class.

2fill in blank

medium

Complete the code to call the instance method from the included module.

Ruby

module Farewell
  def goodbye
    "Goodbye!"
  end
end

class Friend
  include Farewell
end

f = Friend.new
puts f.[1]

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

Afarewell

Bgoodbye

Chello

Dbye

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method not defined in the module.

Using a method name that does not exist on the instance.

The instance method defined in the module is goodbye, so calling f.goodbye works.

3fill in blank

hard

Fix the error by completing the code to include the module correctly.

Ruby

module Helper
  def assist
    "Assisting"
  end
end

class Worker
  [1] Helper
end

w = Worker.new
puts w.assist

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

Aextend

Bimport

Cinclude

Dprepend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'extend' which adds methods as class methods.

Using 'import' which is not a Ruby keyword.

To add instance methods from a module, use include. extend adds class methods.

4fill in blank

hard

Fill both blanks to define a module and include it for instance methods.

Ruby

module [1]
  def greet
    "Hi!"
  end
end

class User
  [2] GreetModule
end

u = User.new
puts u.greet

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

AGreetModule

Bextend

Cinclude

DGreeting

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using a module name that does not match the definition.

The module name is GreetModule and it is included using include to add instance methods.

5fill in blank

hard

Fill all three blanks to create a module, include it, and call its instance method.

Ruby

module [1]
  def welcome
    "Welcome!"
  end
end

class Member
  [2] WelcomeModule
end

m = Member.new
puts m.[3]

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

AWelcomeModule

Binclude

Cwelcome

Dextend

Attempts:

3 left

💡 Hint

Common Mistakes

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

Calling a method name that does not exist in the module.

Mismatching module name in definition and inclusion.

The module is named WelcomeModule, included with include, and the instance method welcome is called on the object.

Practice

1. What does the include keyword do in Ruby when used inside a class?

easy

A. It deletes all methods from the class.

B. It adds the module's methods as class methods to the class.

C. It creates a new module inside the class.

D. It adds the module's methods as instance methods to the class.

Solution

1. Step 1: Understand the role of include

   The include keyword is used to add methods from a module into a class.

2. Step 2: Identify how methods are added

   When a module is included, its methods become instance methods of the class, meaning objects of the class can call them.

3. Final Answer:

   It adds the module's methods as instance methods to the class. -> Option D

4. Quick Check:

   Include = instance methods added [OK]

Hint: Include adds module methods as instance methods [OK]

Common Mistakes:

• Confusing include with extend (which adds class methods)
• Thinking include creates a new module
• Assuming include removes existing methods

2. Which of the following is the correct syntax to include a module named Greetings inside a class Person?

easy

A. class Person; include Greetings; end

B. class Person; extend Greetings; end

C. class Person; include(Greetings); end

D. class Person; use Greetings; end

Solution

1. Step 1: Recall correct syntax for including modules

   In Ruby, to add instance methods from a module, use include ModuleName inside the class body without parentheses.

2. Step 2: Check each option

   class Person; include Greetings; end uses include Greetings correctly. class Person; extend Greetings; end uses extend which adds class methods, not instance methods. class Person; include(Greetings); end uses parentheses which is not standard syntax. class Person; use Greetings; end uses use which is invalid in Ruby.

3. Final Answer:

   class Person; include Greetings; end -> Option A

4. Quick Check:

   Include syntax = include ModuleName [OK]

Hint: Use 'include ModuleName' without parentheses [OK]

Common Mistakes:

• Using extend instead of include
• Adding parentheses after include
• Using invalid keywords like 'use'

3. What will be the output of the following Ruby code?

module Talk
  def speak
    "Hello!"
  end
end

class Dog
  include Talk
end

puts Dog.new.speak

medium

A. NoMethodError

B. Hello!

C. speak

D. nil

Solution

1. Step 1: Understand module inclusion

   The module Talk defines an instance method speak. Including it in Dog adds speak as an instance method of Dog.

2. Step 2: Trace the method call

   Creating a new Dog object and calling speak will execute the method from Talk, returning "Hello!".

3. Final Answer:

   Hello! -> Option B

4. Quick Check:

   Included method called = "Hello!" [OK]

Hint: Included module methods become instance methods [OK]

Common Mistakes:

• Expecting NoMethodError because of missing method
• Confusing instance and class methods
• Thinking output is method name or nil

4. Identify the error in the following Ruby code:

module Walk
  def walk
    "Walking"
  end
end

class Person
  extend Walk
end

puts Person.new.walk

medium

A. NoMethodError because walk is not an instance method

B. SyntaxError due to extend usage

C. No error, outputs "Walking"

D. TypeError because module cannot be extended

Solution

1. Step 1: Understand extend vs include

   Using extend Walk adds module methods as class methods, not instance methods.

2. Step 2: Analyze method call

   Person.new.walk calls walk on an instance, but walk is only a class method here, so it raises NoMethodError.

3. Final Answer:

   NoMethodError because walk is not an instance method -> Option A

4. Quick Check:

   Extend adds class methods, instance call fails [OK]

Hint: Extend adds class methods; instance calls fail [OK]

Common Mistakes:

• Confusing extend with include
• Expecting no error on instance method call
• Thinking extend causes syntax or type errors

5. Given the module and classes below, what will puts Cat.new.sound output?

module AnimalSounds
  def sound
    "Generic sound"
  end
end

class Dog
  include AnimalSounds
  def sound
    "Bark"
  end
end

class Cat
  include AnimalSounds
end

hard

A. Bark

B. NoMethodError

C. Generic sound

D. nil

Solution

1. Step 1: Check method definitions in classes

   Class Dog overrides sound method with "Bark". Class Cat does not override it.

2. Step 2: Determine method lookup for Cat instance

   Since Cat includes AnimalSounds and does not override sound, calling sound on Cat.new uses the module's method returning "Generic sound".

3. Final Answer:

   Generic sound -> Option C

4. Quick Check:

   Included method used if no override [OK]

Hint: Class method overrides module method if defined [OK]

Common Mistakes:

• Assuming Cat uses Dog's sound method
• Expecting NoMethodError for missing method
• Confusing instance and class methods