swift

Swift

Overview

Swift programming patterns including protocols, generics, async/await, and SwiftUI.

Swift Fundamentals

Structs and Classes

import Foundation

// Struct (value type, preferred for most cases)
struct User: Identifiable, Codable {
    let id: UUID
    var email: String
    var name: String
    var createdAt: Date

    // Memberwise initializer provided automatically
    // Custom initializer
    init(email: String, name: String) {
        self.id = UUID()
        self.email = email
        self.name = name
        self.createdAt = Date()
    }

    // Computed property
    var displayName: String {
        "\(name) <\(email)>"
    }

    // Mutating method (for structs)
    mutating func updateEmail(_ newEmail: String) {
        email = newEmail
    }
}

// Class (reference type)
class UserManager {
    static let shared = UserManager() // Singleton

    private var users: [UUID: User] = [:]

    private init() {}

    func add(_ user: User) {
        users[user.id] = user
    }

    func find(id: UUID) -> User? {
        users[id]
    }
}

// Actor (thread-safe reference type)
actor UserStore {
    private var users: [UUID: User] = [:]

    func add(_ user: User) {
        users[user.id] = user
    }

    func find(id: UUID) -> User? {
        users[id]
    }

    func count() -> Int {
        users.count
    }
}

Enums and Pattern Matching

// Enum with associated values
enum Result<Success, Failure: Error> {
    case success(Success)
    case failure(Failure)

    var isSuccess: Bool {
        if case .success = self { return true }
        return false
    }

    func map<NewSuccess>(_ transform: (Success) -> NewSuccess) -> Result<NewSuccess, Failure> {
        switch self {
        case .success(let value):
            return .success(transform(value))
        case .failure(let error):
            return .failure(error)
        }
    }
}

// Enum with raw values
enum Status: String, Codable, CaseIterable {
    case pending = "pending"
    case active = "active"
    case inactive = "inactive"

    var displayName: String {
        switch self {
        case .pending: return "Pending Review"
        case .active: return "Active"
        case .inactive: return "Inactive"
        }
    }
}

// Pattern matching
func process(_ result: Result<User, Error>) {
    switch result {
    case .success(let user) where user.email.contains("@admin"):
        print("Admin user: \(user.name)")
    case .success(let user):
        print("Regular user: \(user.name)")
    case .failure(let error):
        print("Error: \(error.localizedDescription)")
    }
}

// If-case pattern
if case .success(let user) = result {
    print(user.name)
}

// Guard-case pattern
func handleSuccess(_ result: Result<User, Error>) -> User? {
    guard case .success(let user) = result else {
        return nil
    }
    return user
}