**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Object-Oriented Programming (OOP) in Ruby **Topic:** Understanding self and class methods In this topic, we will delve into the world of self and class methods in Ruby, two fundamental concepts that are essential for any object-oriented programmer. By the end of this topic, you will have a deep understanding of how to use self and class methods to create more robust and maintainable code. **What is self?** In Ruby, `self` is a special variable that refers to the current object being executed. It is a shorthand way to access the instance variables and methods of the current object. When you use `self` in a method, it refers to the object that the method is called on. Here is an example: ```ruby class Person def initialize(name) @name = name end def greet puts "Hello, my name is #{self.name}" end end person = Person.new("John") person.greet # Output: Hello, my name is John ``` In this example, `self` is used to access the `@name` instance variable of the `Person` object. **What is class method?** A class method is a method that is called on the class itself, rather than on an instance of the class. Class methods are used to define behavior that is shared by all instances of the class. Here is an example: ```ruby class Person def initialize(name) @name = name end def greet puts "Hello, my name is #{self.name}" end def self.greet_all puts "Hello, everyone!" end end person1 = Person.new("John") person2 = Person.new("Jane") Person.greet_all # Output: Hello, everyone! ``` In this example, `greet_all` is a class method that is called on the `Person` class itself, rather than on an instance of the class. **Key differences between self and class methods** Here are the key differences between `self` and class methods: * `self` refers to the current object being executed, while class methods refer to the class itself. * `self` is used to access instance variables and methods, while class methods are used to define behavior that is shared by all instances of the class. * `self` is called on an instance of the class, while class methods are called on the class itself. **Practical takeaways** Here are some practical takeaways from this topic: * Use `self` to access instance variables and methods of the current object. * Use class methods to define behavior that is shared by all instances of the class. * Be aware of the differences between `self` and class methods, and use them correctly in your code. **Exercise** Write a Ruby program that demonstrates the use of `self` and class methods. Create a class called `Vehicle` with an instance variable `color` and a class method `describe_vehicle`. Use `self` to access the `color` instance variable and the `describe_vehicle` class method. ```ruby # Write your code here ``` **Comment or ask for help** Please leave a comment or ask for help if you have any questions or need further clarification on this topic.