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In Swift, classes and structures are powerful constructs that allow you to create custom data types. Both classes and structures can store values, define methods, and provide functionality to your code. However, they have some key differences that make them suitable for different scenarios.

Key Concepts

Defining Classes and Structures

Class: A blueprint for creating objects (instances). Classes support inheritance, which allows one class to inherit the characteristics of another.
Structure: Similar to classes but do not support inheritance. Structures are value types, meaning they are copied when assigned to a new variable or constant.

Syntax

Class Syntax:

class ClassName {
    // Properties
    var property1: Type
    var property2: Type

    // Initializer
    init(property1: Type, property2: Type) {
        self.property1 = property1
        self.property2 = property2
    }

    // Methods
    func methodName() {
        // Method implementation
    }
}

Structure Syntax:

struct StructName {
    // Properties
    var property1: Type
    var property2: Type

    // Initializer
    init(property1: Type, property2: Type) {
        self.property1 = property1
        self.property2 = property2
    }

    // Methods
    func methodName() {
        // Method implementation
    }
}

Example

Class Example:

class Car {
    var make: String
    var model: String
    var year: Int

    init(make: String, model: String, year: Int) {
        self.make = make
        self.model = model
        self.year = year
    }

    func displayDetails() {
        print("Car: \\(make) \\(model), Year: \\(year)")
    }
}

let myCar = Car(make: "Toyota", model: "Corolla", year: 2020)
myCar.displayDetails()  // Output: Car: Toyota Corolla, Year: 2020

Structure Example:

struct Book {
    var title: String
    var author: String
    var pages: Int

    func description() -> String {
        return "\\(title) by \\(author), \\(pages) pages"
    }
}

let myBook = Book(title: "Swift Programming", author: "Apple Inc.", pages: 500)
print(myBook.description())  // Output: Swift Programming by Apple Inc., 500 pages

Differences Between Classes and Structures

Feature	Class	Structure
Inheritance	Yes	No
Type	Reference type	Value type
Memory Management	Reference counting (ARC)	Copied when assigned or passed
Mutability	Mutable even if assigned to a constant	Immutable if assigned to a constant

Practical Exercises

Exercise 1: Define a Class

Define a class Person with properties name and age, and a method greet that prints a greeting message.

class Person {
    var name: String
    var age: Int

    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }

    func greet() {
        print("Hello, my name is \(name) and I am \(age) years old.")
    }
}

let person = Person(name: "Alice", age: 30)
person.greet()  // Output: Hello, my name is Alice and I am 30 years old.

Exercise 2: Define a Structure

Define a structure Rectangle with properties width and height, and a method area that returns the area of the rectangle.

struct Rectangle {
    var width: Double
    var height: Double

    func area() -> Double {
        return width * height
    }
}

let rectangle = Rectangle(width: 10.0, height: 5.0)
print("Area of rectangle: \(rectangle.area())")  // Output: Area of rectangle: 50.0

Common Mistakes and Tips

Mutability: Remember that structures are immutable when assigned to a constant. If you need to modify properties, use a variable.
Reference vs. Value Types: Be aware of the differences between reference and value types. Classes are reference types, meaning changes to an instance affect all references to that instance. Structures are value types, meaning each instance is independent.

Conclusion

In this section, you learned about the fundamental differences between classes and structures in Swift. You now know how to define and use both constructs, and understand their unique characteristics. This knowledge is crucial as you progress to more advanced topics in Swift, such as inheritance and protocols.

Classes and Structures

Key Concepts

Defining Classes and Structures

Syntax

Example

Differences Between Classes and Structures

Practical Exercises

Exercise 1: Define a Class

Exercise 2: Define a Structure

Common Mistakes and Tips

Conclusion

Swift Programming Course

Module 1: Introduction to Swift

Module 2: Control Flow

Module 3: Functions and Closures

Module 4: Object-Oriented Programming

Module 5: Advanced Swift

Module 6: Swift and iOS Development

Module 7: Final Project