Struct Best Practices

// STRUCT BEST PRACTICES
// Guidelines for writing clean, efficient structs

// ===== 1. USE STRUCTS BY DEFAULT =====
// Prefer structs over classes when possible

// GOOD: Simple data container
struct UserProfile {
    var name: String
    var email: String
    var age: Int
}

// ===== 2. KEEP STRUCTS SMALL & FOCUSED =====
// Single Responsibility Principle

// BAD: Too many responsibilities
struct BadUser {
    var name: String
    var email: String
    func sendEmail() { }
    func validatePassword() { }
    func saveToDatabase() { }
}

// GOOD: Separate concerns
struct User {
    var name: String
    var email: String
}

struct EmailService {
    func send(to user: User, message: String) { }
}

// ===== 3. USE MEANINGFUL NAMES =====
// Clear, descriptive property names

// BAD
struct P {
    var x: Double
    var y: Double
}

// GOOD
struct Coordinate {
    var latitude: Double
    var longitude: Double
}

// ===== 4. PROVIDE DEFAULT VALUES =====
// Make structs easier to initialize

struct Settings {
    var theme: String = "light"
    var fontSize: Int = 14
    var notificationsEnabled: Bool = true
}

let defaultSettings = Settings()
let customSettings = Settings(theme: "dark")

// ===== 5. USE COMPUTED PROPERTIES WISELY =====
// For derived values, not stored data

struct Rectangle {
    var width: Double
    var height: Double

    // GOOD: Derived from stored properties
    var area: Double {
        return width * height
    }

    var perimeter: Double {
        return 2 * (width + height)
    }

    var isSquare: Bool {
        return width == height
    }
}

// ===== 6. MARK MUTATING METHODS EXPLICITLY =====
// Clear intent about what modifies state

struct Counter {
    private(set) var value: Int = 0

    mutating func increment() {
        value += 1
    }

    mutating func reset() {
        value = 0
    }

    // Non-mutating returns new instance
    func adding(_ amount: Int) -> Counter {
        return Counter(value: value + amount)
    }
}

// ===== 7. USE ACCESS CONTROL =====
// Hide implementation details

struct BankAccount {
    private(set) var balance: Double = 0

    mutating func deposit(_ amount: Double) {
        guard amount > 0 else { return }
        balance += amount
    }

    mutating func withdraw(_ amount: Double) -> Bool {
        guard amount > 0 && balance >= amount else {
            return false
        }
        balance -= amount
        return true
    }
}

// ===== 8. CONFORM TO PROTOCOLS =====
// Add functionality through protocols

struct Task: Identifiable, Equatable, Codable {
    let id: UUID
    var title: String
    var isCompleted: Bool

    init(title: String) {
        self.id = UUID()
        self.title = title
        self.isCompleted = false
    }
}

// ===== 9. USE EXTENSIONS FOR ORGANIZATION =====
// Group related functionality

struct Product {
    var name: String
    var price: Double
}

extension Product: CustomStringConvertible {
    var description: String {
        return "\(name): $\(price)"
    }
}

extension Product {
    func withDiscount(_ percent: Double) -> Product {
        let newPrice = price * (1 - percent / 100)
        return Product(name: name, price: newPrice)
    }
}

// ===== 10. DOCUMENT YOUR CODE =====
/// A struct representing a geographic location
struct Location {
    /// Latitude in degrees (-90 to 90)
    var latitude: Double

    /// Longitude in degrees (-180 to 180)
    var longitude: Double

    /// Calculates distance to another location in kilometers
    func distance(to other: Location) -> Double {
        // Haversine formula implementation
        return 0.0  // Simplified
    }
}