Constants in classes in Ruby - Mini Project: Build & Apply

Constants in classes

📖 Scenario: Imagine you are creating a simple program to manage information about cars. Each car has a brand and a fixed number of wheels. The number of wheels is always the same for all cars, so it makes sense to store it as a constant inside the class.

🎯 Goal: You will create a class called Car with a constant WHEELS set to 4. Then you will create a method to display the number of wheels and the brand of the car.

📋 What You'll Learn

Create a class called Car

Inside the class, define a constant WHEELS with the value 4

Add an initialize method that takes a brand parameter and saves it

Add a method display_info that prints the brand and the number of wheels

Create an instance of Car with brand "Toyota"

Call the display_info method on the instance

💡 Why This Matters

🌍 Real World

Constants in classes are useful to store values that do not change, like fixed settings or properties shared by all objects of that class.

💼 Career

Understanding constants in classes helps you write clear and maintainable code, which is important in software development jobs.

1

Create the Car class with a brand attribute

Create a class called Car with an initialize method that takes a parameter brand and saves it in an instance variable @brand.

Ruby

class Car
  # Your code here
end

Need a hint?

Remember to use def initialize(brand) and assign @brand = brand.

2

Add a constant WHEELS with value 4

Inside the Car class, add a constant called WHEELS and set it to 4.

Ruby

class Car
  WHEELS = 4

  def initialize(brand)
    @brand = brand
  end
end
# Your code here

Need a hint?

Constants in Ruby start with a capital letter. Write WHEELS = 4 inside the class.

3

Add a method to display brand and wheels

Add a method called display_info inside the Car class that prints the brand and the number of wheels using puts. Use @brand for the brand and Car::WHEELS to access the constant.

Ruby

class Car
  WHEELS = 4

  def initialize(brand)
    @brand = brand
  end

  # Your code here
end

Need a hint?

Use def display_info and inside it write puts "Brand: #{@brand}, Wheels: #{Car::WHEELS}".

4

Create a Car instance and call display_info

Create a variable my_car and assign it a new Car object with brand "Toyota". Then call my_car.display_info to print the information.

Ruby

class Car
  WHEELS = 4

  def initialize(brand)
    @brand = brand
  end

  def display_info
    puts "Brand: #{@brand}, Wheels: #{Car::WHEELS}"
  end
end

# Your code here

Need a hint?

Create my_car = Car.new("Toyota") and then call my_car.display_info.