**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Object-Oriented Programming (OOP) in Ruby **Topic:** Introduction to classes and objects **Introduction** In the previous topics, we have covered the basics of Ruby programming, including variables, data types, operators, control structures, functions, and scope. Now, it's time to dive into the world of Object-Oriented Programming (OOP) in Ruby. OOP is a programming paradigm that revolves around the concept of objects and classes. In this topic, we will explore the basics of classes and objects in Ruby, including how to define, create, and use them. **What are Classes and Objects?** In OOP, a class is a blueprint or a template that defines the properties and behavior of an object. An object is an instance of a class, and it has its own set of attributes (data) and methods (functions). Think of a class as a cookie cutter, and an object as a cookie made from that cutter. Just as a cookie cutter defines the shape and size of a cookie, a class defines the properties and behavior of an object. **Defining a Class in Ruby** In Ruby, a class is defined using the `class` keyword followed by the name of the class. For example: ```ruby class Car # class definition end ``` This defines a class called `Car`. **Creating an Object from a Class** To create an object from a class, we use the `new` method. For example: ```ruby car = Car.new ``` This creates a new object called `car` from the `Car` class. **Attributes and Methods** In Ruby, attributes are defined using the `attr_accessor` method, which allows us to access and modify the attributes of an object. Methods are defined using the `def` keyword, which allows us to define functions that can be called on an object. For example: ```ruby class Car attr_accessor :color, :model def initialize(color, model) @color = color @model = model end def honk puts "Honk honk!" end end ``` This defines a class called `Car` with two attributes: `color` and `model`. It also defines an `initialize` method to set the initial values of the attributes, and a `honk` method to make the car honk. **Creating an Object and Calling Methods** We can create an object from the `Car` class and call its methods like this: ```ruby car = Car.new("red", "Toyota") puts car.color # prints "red" puts car.model # prints "Toyota" car.honk # prints "Honk honk!" ``` **Key Concepts** * A class is a blueprint or a template that defines the properties and behavior of an object. * An object is an instance of a class, and it has its own set of attributes and methods. * Attributes are defined using the `attr_accessor` method, and methods are defined using the `def` keyword. * We can create an object from a class using the `new` method, and call its methods using dot notation. **Practical Takeaways** * Use the `class` keyword to define a class in Ruby. * Use the `new` method to create an object from a class. * Use the `attr_accessor` method to define attributes, and the `def` keyword to define methods. * Use dot notation to call methods on an object. **Exercise** Create a class called `Person` with attributes for `name` and `age`. Define methods to set and get these attributes, and to print out a greeting message. **Leave a comment or ask for help if you have any questions or need further clarification!** [External Links] * Ruby documentation: [https://ruby-doc.org/](https://ruby-doc.org/) * Ruby classes and objects tutorial: [https://www.w3schools.com/ruby/ruby_classes.asp](https://www.w3schools.com/ruby/ruby_classes.asp) Note: The above content is a detailed and comprehensive explanation of the topic "Introduction to classes and objects" in Ruby programming. It includes examples, key concepts, practical takeaways, and an exercise to help students grasp and apply the material effectively.