Initialize method as constructor in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code with initialize method?

Look at this Ruby class with an initialize method. What will be printed when we create a new object?

Ruby

class Person
  def initialize(name)
    @name = name
  end

  def greet
    "Hello, #{@name}!"
  end
end

person = Person.new("Alice")
puts person.greet

A Hello, !

B Hello, @name!

C Hello, Alice!

D Error: undefined method `greet`

💡 Hint

Remember, initialize sets instance variables when creating a new object.

The initialize method sets @name to "Alice". The greet method uses this variable to print "Hello, Alice!".

❓ Predict Output

intermediate

What happens if initialize method is missing?

What will happen if we try to create a new object with an argument but the class has no initialize method?

Ruby

class Car
  def start
    "Car started"
  end
end

car = Car.new("Toyota")
puts car.start

A Car started

B ArgumentError: wrong number of arguments (given 1, expected 0)

C NoMethodError: undefined method `start`

D nil

💡 Hint

If you pass arguments to new but no initialize accepts them, Ruby raises an error.

The default initialize takes no arguments. Passing "Toyota" causes an ArgumentError.

🔧 Debug

advanced

Why does this initialize method cause an error?

Find the error in this Ruby class and explain why it happens.

Ruby

class Book
  def initialize(title)
    @title = title
  end

  def show_title
    "Title: #{@title}"
  end
end

book = Book.new("Ruby Guide")
puts book.show_title

A SyntaxError: unexpected local variable assignment

B Prints: Title: Ruby Guide

C Prints: Title:

D NameError: undefined local variable or method `title`

💡 Hint

Check how instance variables are assigned and accessed in Ruby.

The code assigns to a local variable title inside initialize, not to an instance variable @title. The method show_title tries to use title which is undefined in that scope, causing a NameError.

🧠 Conceptual

advanced

What is the role of the initialize method in Ruby classes?

Choose the best description of what the initialize method does in Ruby.

A It is called automatically when a new object is created to set up initial values.

B It defines a method that must be called manually after creating an object.

C It is used to destroy objects and free memory.

D It is a special method that runs only when the program ends.

💡 Hint

Think about what happens when you write ClassName.new.

The initialize method runs automatically during object creation to set up instance variables or other setup tasks.

❓ Predict Output

expert

What is the output of this Ruby code with multiple initialize parameters?

Analyze this Ruby class with multiple parameters in initialize. What will be printed?

Ruby

class Rectangle
  def initialize(width, height)
    @width = width
    @height = height
  end

  def area
    @width * @height
  end
end

rect = Rectangle.new(5, 3)
puts rect.area

A 15

B 53

C Error: wrong number of arguments (given 2, expected 1)

D 0

💡 Hint

Multiply width and height stored in instance variables.

The initialize method sets @width to 5 and @height to 3. The area method returns 5 * 3 = 15.