Struct Basics

// WHAT IS A STRUCT?
// A struct is a custom data type that groups related values
// Structs are VALUE TYPES (copied when assigned)

// BASIC STRUCT DEFINITION
struct Person {
    var name: String
    var age: Int
}

// CREATING INSTANCES
var person1 = Person(name: "Alice", age: 25)
var person2 = Person(name: "Bob", age: 30)

print(person1.name)  // Alice
print(person2.age)   // 30

// ACCESSING & MODIFYING PROPERTIES
person1.age = 26
print(person1.age)   // 26

// VALUE TYPE BEHAVIOR
var person3 = person1  // Creates a COPY
person3.name = "Charlie"

print(person1.name)  // Alice (unchanged!)
print(person3.name)  // Charlie

// STRUCT WITH DIFFERENT PROPERTY TYPES
struct Product {
    var name: String
    var price: Double
    var inStock: Bool
    var quantity: Int
}

let laptop = Product(
    name: "MacBook Pro",
    price: 1999.99,
    inStock: true,
    quantity: 50
)

print("\(laptop.name): $\(laptop.price)")

// STRUCT WITH DEFAULT VALUES
struct User {
    var username: String
    var email: String
    var isActive: Bool = true  // Default value
    var loginCount: Int = 0    // Default value
}

// Can omit properties with defaults
let user1 = User(username: "swift_fan", email: "[email protected]")
print(user1.isActive)  // true (default)

// Or override them
let user2 = User(
    username: "admin",
    email: "[email protected]",
    isActive: true,
    loginCount: 100
)

// WHY USE STRUCTS?
// 1. Group related data together
// 2. Create custom types
// 3. Value semantics (safer in multi-threaded code)
// 4. Lightweight and fast

// COMMON BUILT-IN STRUCTS
// String, Int, Double, Bool, Array, Dictionary
// are all structs in Swift!

let greeting: String = "Hello"  // String is a struct!
let numbers: [Int] = [1, 2, 3]  // Array is a struct!