// Immutable User in Swift (Using let + Struct for True Immutability)
//
// Swift enforces immutability through:
//
// 1. `let` → prevents reassignment of variables
// 2. `struct` → value types; cannot mutate unless declared `var`
// 3. `let` properties inside a struct → fully immutable fields
// 4. No setters → no mutation path
//
// Attempting to modify an immutable struct or its properties
// results in a compile-time error.
//
// Immutable User using a struct with let properties
struct User {
let id: Int
let name: String
}
func main() {
// Immutable user
let user = User(id: 42, name: "Ella")
print("ID: \(user.id)")
print("Name: \(user.name)")
// Attempt 1: modify id
// user.id = 100 // ERROR: Cannot assign to property: 'id' is a 'let' constant
// Attempt 2: modify name
// user.name = "Lucas" // ERROR: Cannot assign to property: 'name' is a 'let' constant
// Attempt 3: reassign user
// user = User(id: 100, name: "Lucas") // ERROR: Cannot assign to value: 'user' is a 'let' constant
// Instead, Swift uses a new instance to represent changes
let updatedUser = User(id: user.id, name: "Lucas")
print("Updated Name (new instance): \(updatedUser.name)")
print("Original Name: \(user.name)")
}
main()
/*
run:
ID: 42
Name: Ella
Updated Name (new instance): Lucas
Original Name: Ella
*/
