Module methods in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a module method that returns a greeting string.

Ruby

module Greeter
  def self.[1]
    "Hello!"
  end
end

puts Greeter.greet

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

Agreet

Bhello

Cgreeting

Dsay_hello

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name different from the one called on the module.

Defining an instance method instead of a module method.

The method name greet matches the call Greeter.greet, so it correctly defines the module method.

2fill in blank

medium

Complete the code to call the module method correctly.

Ruby

module Calculator
  def self.square(x)
    x * x
  end
end

result = Calculator.[1](4)
puts result

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

Apower

Bsquare_root

Cmultiply

Dsquare

Attempts:

3 left

💡 Hint

Common Mistakes

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

Trying to call the method without the module name.

The method square is defined as a module method and called with Calculator.square(4).

3fill in blank

hard

Fix the error in the module method definition to make it a proper module method.

Ruby

module Printer
  def [1](text)
    puts text
  end
end

Printer.print("Hello")

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

Aprint

Bself.print

CPrint

Dprinter

Attempts:

3 left

💡 Hint

Common Mistakes

Defining the method without self. and expecting to call it on the module.

Using incorrect capitalization for method names.

To define a module method, prefix the method name with self.. This makes it callable on the module itself.

4fill in blank

hard

Fill both blanks to define and call a module method that returns the sum of two numbers.

Ruby

module MathOps
  def [1](a, b)
    a [2] b
  end
end

puts MathOps.add(3, 4)

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

Aself.add

Bsubtract

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Defining the method without self..

Using the wrong operator for addition.

The method is defined as self.add to be a module method, and it returns the sum using the + operator.

5fill in blank

hard

Fill all three blanks to define a module method that checks if a number is even and call it.

Ruby

module NumberCheck
  def [1](num)
    num [2] 2 == 0
  end
end

puts NumberCheck.[3](10)

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

Aself.even?

B%

Ceven?

Dis_even

Attempts:

3 left

💡 Hint

Common Mistakes

Defining the method without self..

Using the wrong operator instead of modulo.

Calling the method with a different name than defined.

The method is defined as self.even? to be a module method. It uses the modulo operator % to check if the number is divisible by 2. The method is called as NumberCheck.even?(10).

Practice

1. What is the correct way to define a method inside a Ruby module so it can be called directly on the module?

easy

A. Define the method outside the module

B. Define the method without self inside the module

C. Define the method with self.method_name inside the module

D. Define the method with def module.method_name inside the module

Solution

1. Step 1: Understand module method definition

   In Ruby, to make a method callable directly on a module, you define it with self.method_name inside the module.

2. Step 2: Compare options

   Define the method with self.method_name inside the module uses self.method_name, which is correct. Other options either omit self or use invalid syntax.

3. Final Answer:

   Define the method with self.method_name inside the module -> Option C

4. Quick Check:

   Module methods use self.method_name = A [OK]

Hint: Use self.method_name to define module methods [OK]

Common Mistakes:

• Forgetting to add self before method name
• Defining methods outside the module
• Using invalid syntax like def module.method_name

2. Which of the following is the correct syntax to call a module method named greet defined in module Welcome?

easy

A. Welcome#greet

B. greet.Welcome

C. Welcome.new.greet

D. Welcome.greet

Solution

1. Step 1: Recall how to call module methods

   Module methods are called using dot notation: ModuleName.method_name.

2. Step 2: Check options

   Welcome.greet is the correct syntax using dot notation. Welcome#greet incorrectly uses #. greet.Welcome reverses the order. Welcome.new.greet confuses it with an instance method call.

3. Final Answer:

   Welcome.greet -> Option D

4. Quick Check:

   Call module methods with dot = D [OK]

Hint: Call module methods with ModuleName.method_name [OK]

Common Mistakes:

• Using # instead of . to call module methods
• Trying to call method with invalid syntax
• Confusing instance and module method calls

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

module MathTools
  def self.square(x)
    x * x
  end
end

puts MathTools.square(4)

medium

A. 16

B. square

C. Error: undefined method

D. 4

Solution

1. Step 1: Understand the method definition

   The method square is defined as a module method using self.square. It returns the square of the input.

2. Step 2: Calculate the output

   Calling MathTools.square(4) returns 4 * 4 = 16, which is printed.

3. Final Answer:

   16 -> Option A

4. Quick Check:

   4 squared = 16 [OK]

Hint: Multiply input by itself in module method [OK]

Common Mistakes:

• Forgetting self and causing undefined method error
• Confusing output with input
• Expecting method name as output

4. Identify the error in this Ruby module method code:

module Greetings
  def greet
    "Hello!"
  end
end

puts Greetings.greet

medium

A. Method greet is not defined as a module method

B. Module name is incorrect

C. Missing parentheses in method call

D. Syntax error in method body

Solution

1. Step 1: Check method definition inside module

   The method greet is defined without self., so it is an instance method, not a module method.

2. Step 2: Understand method call

   Calling Greetings.greet tries to call a module method, but none exists, causing an error.

3. Final Answer:

   Method greet is not defined as a module method -> Option A

4. Quick Check:

   Missing self. means no module method [OK]

Hint: Add self. to define module methods [OK]

Common Mistakes:

• Defining instance methods instead of module methods
• Calling module method without defining it
• Assuming parentheses are required in method call

5. Given the module below, how can you add a module method double that returns twice the input number?

module Calculator
  # Add your method here
end

hard

A. def double(x)
x + x
end

B. def self.double(x)
x * 2
end

C. def Calculator.double(x)
x * 2
end

D. def self.double
x * 2
end

Solution

1. Step 1: Define a module method with self

   To create a module method, define it with self.method_name inside the module.

2. Step 2: Write method to return twice the input

   The method should take one argument x and return x * 2.

3. Final Answer:

   def self.double(x) x * 2 end -> Option B

4. Quick Check:

   Module method with self and correct logic = A [OK]

Hint: Use def self.method(args) for module methods [OK]

Common Mistakes:

• Omitting self and creating instance method
• Missing method argument
• Defining method outside module