Why class-level behavior matters in Ruby - See It in Action

Why class-level behavior matters

📖 Scenario: Imagine you are creating a simple system to track books in a library. Each book has a title and an author. You want to count how many books have been created in total, no matter which book it is.

🎯 Goal: You will build a Ruby class Book that keeps track of how many book objects have been created using class-level behavior.

📋 What You'll Learn

Create a class called Book

Add an instance method initialize that takes title and author parameters

Add a class variable @@count to count how many books have been created

Increment @@count each time a new Book is created

Add a class method self.count that returns the total number of books created

Create at least two Book objects with given titles and authors

Print the total number of books created using the class method

💡 Why This Matters

🌍 Real World

Counting objects like books, users, or orders is common in software to track totals or limits.

💼 Career

Understanding class-level behavior is important for designing classes that manage shared data or resources in Ruby applications.

1

Create the Book class with initialize method

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

Ruby

class Book
  def initialize(title, author)
    # Your code here
  end
end

Need a hint?

Use @title and @author to store the values inside the object.

2

Add a class variable to count books

Inside the Book class, add a class variable @@count and set it to 0 before the initialize method.

Ruby

class Book
  @@count = 0
  def initialize(title, author)
    @title = title
    @author = author
  end
end
# Your code here

Need a hint?

Class variables start with @@ and are shared by all instances.

3

Increment count when a book is created

Inside the initialize method, add code to increase @@count by 1 each time a new Book object is created.

Ruby

class Book
  @@count = 0
  def initialize(title, author)
    @title = title
    @author = author
    # Your code here
  end
end

Need a hint?

Use @@count += 1 to add one to the class variable.

4

Add class method and print total books

Add a class method self.count inside the Book class that returns @@count. Then create two Book objects with titles '1984' and 'Brave New World' and authors 'George Orwell' and 'Aldous Huxley'. Finally, print the total number of books created by calling Book.count.

Ruby

class Book
  @@count = 0
  def initialize(title, author)
    @title = title
    @author = author
    @@count += 1
  end

  # Your code here
end

# Create two Book objects

# Print total books created

Need a hint?

Define def self.count to make a class method. Use puts Book.count to print the total.