**Course Title:** Swift Programming: From Basics to Advanced Development **Section Title:** Object-Oriented Programming (OOP) in Swift **Topic:** Properties and methods, initializers and deinitializers **Introduction** In the previous topic, we learned how to define classes and structures in Swift. In this topic, we'll explore how to add properties and methods to these classes and structures. We'll also learn about initializers and deinitializers, which are used to set up and clean up resources when instances are created and destroyed. **Properties** Properties are values that are associated with an instance of a class or structure. They can be used to store and retrieve data, and they can also be used to calculate values on the fly. There are two types of properties in Swift: stored properties and computed properties. **Stored Properties** Stored properties are stored as part of an instance, and they can be accessed directly using dot notation. ```swift class Person { var name: String = "John" var age: Int = 30 } var person = Person() person.name = "Jane" print(person.name) // prints "Jane" ``` **Computed Properties** Computed properties are calculated on the fly when they are accessed. They do not store a value themselves, and they can be used to implement read-only properties. ```swift class Person { var name: String = "John" var age: Int = 30 var description: String { return "\(name) is \(age) years old" } } var person = Person() print(person.description) // prints "John is 30 years old" ``` **Property Observers** Property observers are functions that are called when a property's value changes. They can be used to respond to changes in a property's value. ```swift class Person { var name: String = "John" { didSet { print("Name changed to \(name)") } } } var person = Person() person.name = "Jane" // prints "Name changed to Jane" ``` **Methods** Methods are functions that belong to an instance of a class or structure. They can be used to perform actions on an instance. ```swift class Person { var name: String = "John" var age: Int = 30 func greet() { print("Hello, my name is \(name)") } } var person = Person() person.greet() // prints "Hello, my name is John" ``` **Initializers** Initializers are used to set up an instance of a class or structure. They can be used to initialize properties and perform other setup tasks. ```swift class Person { var name: String var age: Int init(name: String, age: Int) { self.name = name self.age = age } } var person = Person(name: "John", age: 30) print(person.name) // prints "John" ``` **Deinitializers** Deinitializers are used to clean up resources when an instance of a class or structure is destroyed. They can be used to release memory, close files, and perform other cleanup tasks. ```swift class Person { var name: String var age: Int deinit { print("Person is being destroyed") } init(name: String, age: Int) { self.name = name self.age = age } } var person: Person? = Person(name: "John", age: 30) print(person!.name) // prints "John" person = nil // prints "Person is being destroyed" ``` **Best Practices** Here are some best practices to keep in mind when working with properties and methods: * Use stored properties to store data that needs to be retained. * Use computed properties to calculate values on the fly. * Use property observers to respond to changes in a property's value. * Use methods to perform actions on an instance. * Use initializers to set up an instance of a class or structure. * Use deinitializers to clean up resources when an instance of a class or structure is destroyed. **Conclusion** In this topic, we learned about properties and methods, initializers and deinitializers. We learned about the different types of properties and methods, and we saw how to use them to store and retrieve data, perform actions on an instance, and set up and clean up resources. **Additional Resources** For more information on properties and methods, check out the [Apple Developer Documentation on Properties](https://docs.swift.org/swift-book/LanguageGuide/Properties.html). **Leave a Comment or Ask for Help** If you have any questions or need further clarification on any of the topics covered, feel free to leave a comment below. I'll be happy to help. Next, we'll cover **Inheritance, polymorphism, and encapsulation** in Swift.