Open classes (reopening classes) in Ruby - Mini Project: Build & Apply

Open Classes in Ruby: Reopening Classes

📖 Scenario: Imagine you have a simple Ruby program that uses a class to represent a book. Later, you want to add a new feature to this class without changing the original code. Ruby lets you reopen classes to add or change methods anytime.

🎯 Goal: You will create a class called Book, then reopen it to add a new method. Finally, you will print the result of calling this new method on a Book object.

📋 What You'll Learn

Create a class called Book with an initialize method that takes title and author parameters and saves them as instance variables.

Create an instance of Book with title 'Ruby Basics' and author 'Jane Doe'.

Reopen the Book class to add a method called description that returns a string combining the title and author.

Print the result of calling description on the Book instance.

💡 Why This Matters

🌍 Real World

Reopening classes lets developers add or fix features in existing code without rewriting it. This is useful when working with libraries or frameworks.

💼 Career

Understanding open classes is important for Ruby developers to customize behavior and maintain code efficiently.

1

Create the Book class with initialize

Create a class called Book with an initialize method that takes title and author parameters and assigns them to instance variables @title and @author.

Ruby

# Your code here

Need a hint?

Use class Book to start the class. Define initialize with two parameters. Use @title = title and @author = author inside the method.

2

Create a Book instance

Create a variable called my_book and assign it a new Book object with title 'Ruby Basics' and author 'Jane Doe'.

Ruby

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

# Your code here

Need a hint?

Use my_book = Book.new('Ruby Basics', 'Jane Doe') to create the object.

3

Reopen Book class to add description method

Reopen the Book class and add a method called description that returns a string in the format: "Title: [title], Author: [author]" using the instance variables @title and @author.

Ruby

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

my_book = Book.new('Ruby Basics', 'Jane Doe')

# Your code here

Need a hint?

Write class Book again to reopen it. Define def description and return the formatted string using "Title: #{@title}, Author: #{@author}".

4

Print the description of my_book

Write a puts statement to print the result of calling description on the my_book object.

Ruby

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

my_book = Book.new('Ruby Basics', 'Jane Doe')

class Book
  def description
    "Title: #{@title}, Author: #{@author}"
  end
end

# Your code here

Need a hint?

Use puts my_book.description to print the description.