Swift / iOS Development
Project Setup
Swift Package Manager
# Initialize new package
swift package init --type executable
# Add dependencies to Package.swift
# swift package update
Package.swift
// swift-tools-version: 5.10
import PackageDescription
let package = Package(
name: "MyApp",
platforms: [.iOS(.v17), .macOS(.v14)],
products: [
.library(name: "MyApp", targets: ["MyApp"]),
],
dependencies: [
// Add dependencies here
],
targets: [
.target(name: "MyApp", dependencies: []),
.testTarget(name: "MyAppTests", dependencies: ["MyApp"]),
]
)
Xcode Project
# Create new Xcode project via Xcode or:
# Use SwiftUI App template for new projects
# Target iOS 17+ for latest APIs
Type Patterns
Optionals
// Safe unwrapping
if let user = optionalUser {
print(user.name)
}
// Guard for early exit
guard let user = optionalUser else {
return
}
// Optional chaining
let name = user?.profile?.displayName ?? "Anonymous"
// Nil coalescing
let displayName = user?.name ?? "Guest"
Result Type
enum NetworkError: Error {
case invalidURL
case noData
case decodingFailed
}
func fetchUser(id: String) async -> Result<User, NetworkError> {
guard let url = URL(string: "https://api.example.com/users/\(id)") else {
return .failure(.invalidURL)
}
do {
let (data, _) = try await URLSession.shared.data(from: url)
let user = try JSONDecoder().decode(User.self, from: data)
return .success(user)
} catch {
return .failure(.decodingFailed)
}
}
// Usage
switch await fetchUser(id: "123") {
case .success(let user):
print("Got user: \(user.name)")
case .failure(let error):
print("Error: \(error)")
}
Protocols & Extensions
protocol Identifiable {
var id: UUID { get }
}
protocol Displayable {
var displayName: String { get }
}
extension User: Identifiable, Displayable {
var displayName: String {
"\(firstName) \(lastName)"
}
}
Error Handling
// Throwing functions
func loadConfig() throws -> Config {
guard let data = FileManager.default.contents(atPath: configPath) else {
throw ConfigError.fileNotFound
}
return try JSONDecoder().decode(Config.self, from: data)
}
// Do-catch
do {
let config = try loadConfig()
print(config)
} catch ConfigError.fileNotFound {
print("Config file missing")
} catch {
print("Unknown error: \(error)")
}
// Try? for optional result
let config = try? loadConfig()
// Try! only when failure is impossible
let bundledConfig = try! loadBundledConfig()
Async/Await Patterns
Basic Async
func fetchUsers() async throws -> [User] {
let (data, _) = try await URLSession.shared.data(from: usersURL)
return try JSONDecoder().decode([User].self, from: data)
}
// Calling async functions
Task {
do {
let users = try await fetchUsers()
await MainActor.run {
self.users = users
}
} catch {
print("Failed: \(error)")
}
}
Structured Concurrency
// Parallel execution
async let users = fetchUsers()
async let posts = fetchPosts()
let (userList, postList) = try await (users, posts)
// Task groups
func fetchAllUserData(ids: [String]) async throws -> [UserData] {
try await withThrowingTaskGroup(of: UserData.self) { group in
for id in ids {
group.addTask {
try await fetchUserData(id: id)
}
}
return try await group.reduce(into: []) { $0.append($1) }
}
}
Actors
actor UserCache {
private var cache: [String: User] = [:]
func get(_ id: String) -> User? {
cache[id]
}
func set(_ user: User) {
cache[user.id] = user
}
}
// Usage
let cache = UserCache()
await cache.set(user)
let cached = await cache.get("123")
SwiftUI Patterns
View with State
struct ContentView: View {
@State private var count = 0
@State private var username = ""
var body: some View {
VStack(spacing: 16) {
Text("Count: \(count)")
.font(.title)
Button("Increment") {
count += 1
}
TextField("Username", text: $username)
.textFieldStyle(.roundedBorder)
}
.padding()
}
}
Observable ViewModel
@Observable
class UserViewModel {
var users: [User] = []
var isLoading = false
var error: Error?
func loadUsers() async {
isLoading = true
defer { isLoading = false }
do {
users = try await userService.fetchAll()
} catch {
self.error = error
}
}
}
struct UserListView: View {
@State private var viewModel = UserViewModel()
var body: some View {
List(viewModel.users) { user in
UserRow(user: user)
}
.task {
await viewModel.loadUsers()
}
.overlay {
if viewModel.isLoading {
ProgressView()
}
}
}
}
Environment & Dependency Injection
// Define environment key
struct UserServiceKey: EnvironmentKey {
static let defaultValue: UserService = .live
}
extension EnvironmentValues {
var userService: UserService {
get { self[UserServiceKey.self] }
set { self[UserServiceKey.self] = newValue }
}
}
// Use in view
struct ProfileView: View {
@Environment(\.userService) private var userService
var body: some View {
// Use userService
}
}
Testing
Swift Testing (Swift 6+)
import Testing
@Suite("UserService Tests")
struct UserServiceTests {
let service = UserService()
@Test("creates user with valid email")
func createUser() async throws {
let user = try await service.create(email: "test@example.com")
#expect(user.email == "test@example.com")
}
@Test("throws on invalid email")
func invalidEmail() async {
await #expect(throws: ValidationError.self) {
try await service.create(email: "invalid")
}
}
@Test("fetches user by ID", arguments: ["user1", "user2", "user3"])
func fetchUser(id: String) async throws {
let user = try await service.fetch(id: id)
#expect(user.id == id)
}
}
XCTest (Legacy)
import XCTest
@testable import MyApp
final class UserServiceTests: XCTestCase {
var service: UserService!
override func setUp() {
super.setUp()
service = UserService()
}
func testCreateUser() async throws {
let user = try await service.create(email: "test@example.com")
XCTAssertEqual(user.email, "test@example.com")
}
func testInvalidEmailThrows() async {
do {
_ = try await service.create(email: "invalid")
XCTFail("Expected error")
} catch {
XCTAssertTrue(error is ValidationError)
}
}
}
Tooling
# SwiftLint (linting)
brew install swiftlint
swiftlint lint
swiftlint lint --fix
# SwiftFormat (formatting)
brew install swiftformat
swiftformat .
swiftformat . --lint
# Run tests
swift test
xcodebuild test -scheme MyApp -destination 'platform=iOS Simulator,name=iPhone 15'
# Build
swift build
xcodebuild build -scheme MyApp
# fastlane (CI/CD)
brew install fastlane
fastlane init
fastlane ios test
fastlane ios beta # Deploy to TestFlight
.swiftlint.yml
disabled_rules:
- trailing_whitespace
- line_length
opt_in_rules:
- empty_count
- empty_string
excluded:
- Pods
- .build
.swiftformat
--indent 4
--allman false
--wraparguments before-first
--wrapparameters before-first
--self remove
--importgrouping alphabetized
