**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Object-Oriented Programming (OOP) in Ruby **Topic:** Attributes and methods: Getter and setter methods. **Introduction** In Ruby, classes and objects are fundamental concepts that allow us to define and manipulate data. In the previous topic, we introduced classes and objects. Now, we'll dive deeper into the core components of a class: attributes and methods. Specifically, we'll explore getter and setter methods, which are used to access and modify an object's attributes. **Attributes in Ruby** In Ruby, attributes are variables that are associated with an object. They are used to store data that defines the state of the object. Attributes are also known as instance variables or ivars. When you create an object from a class, you can assign values to its attributes using setter methods. **Getter Methods** Getter methods are used to retrieve the value of an attribute. In Ruby, getter methods are created using the `attr_reader` or `def` keywords. Here's an example: ```ruby class Person attr_reader :name def initialize(name) @name = name end end person = Person.new("John Doe") puts person.name # Output: John Doe ``` In the above example, we define a `Person` class with an attribute called `name`. We use the `attr_reader` keyword to create a getter method that allows us to access the `name` attribute. You can also use the `def` keyword to define a getter method: ```ruby class Person def initialize(name) @name = name end def name @name end end person = Person.new("John Doe") puts person.name # Output: John Doe ``` **Setter Methods** Setter methods are used to modify the value of an attribute. In Ruby, setter methods are created using the `attr_writer` or `def` keywords. Here's an example: ```ruby class Person attr_writer :name def initialize(name) @name = name end end person = Person.new("John Doe") person.name = "Jane Doe" puts person.name # Output: Jane Doe (Note: This won't work as attr_writer doesn't create a getter method) ``` However, in the above example, using `attr_writer` alone won't work because we need to retrieve the value using a getter method. To assign value directly using the `=` operator we can create a setter method: ```ruby class Person def initialize(name) @name = name end def name=(value) @name = value end end person = Person.new("John Doe") person.name = "Jane Doe" puts person.name # (Note: This won't work as we didn't create a getter method yet) ``` In the above example, we use the `def` keyword to define a setter method called `name=`, which allows us to assign a new value to the `name` attribute. You can create a getter and setter method using `attr_accessor` in one go: ```ruby class Person attr_accessor :name def initialize(name) @name = name end end person = Person.new("John Doe") person.name = "Jane Doe" puts person.name # Output: Jane Doe ``` **Key Takeaways** * In Ruby, attributes are variables associated with an object. * Getter methods are used to retrieve the value of an attribute. * Setter methods are used to modify the value of an attribute. * The `attr_reader` keyword creates getter methods. * The `attr_writer` keyword creates setter methods. * The `attr_accessor` keyword creates both getter and setter methods. **Practice Exercise** Create a class called `Vehicle` with attributes `make`, `model`, and `year`. Create getter and setter methods for each attribute using `attr_accessor`. **External Resources** For more information on attributes and methods in Ruby, refer to the following resources: * Ruby Documentation: [Attributes](https://ruby-doc.org/core-3.0.0/Module.html#method-i-attr_accessor) * Ruby Programming Language: [Attributes and Methods](https://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Method_Calls) * Codecademy: [Ruby Attributes and Methods](https://www.codecademy.com/learn/learn-ruby/modules/learn-ruby-attributes-and-methods) **Leave a comment or ask for help if you have any questions or need further clarification.**