swift-coding-standards

Swift Coding Standards

Learn Once, Write Anywhere: Master Swift coding standards for iOS, macOS, watchOS, and tvOS development with protocol-oriented design, value semantics, and modern concurrency.

Level 1: Quick Reference

Optionals Cheat Sheet

// Optional binding (safe unwrapping)
if let name = name { print("Hello, \(name)") }

// Guard statement (early exit)
guard let age = age else { return }

// Nil coalescing (default value)
let displayName = name ?? "Anonymous"

// Optional chaining
let count = user?.profile?.posts?.count

Essential Patterns

// Protocol definition with default implementation
protocol Drawable {
    var color: Color { get set }
    func draw()
}

extension Drawable {
    func draw() { print("Drawing with \(color)") }
}

// Struct with protocol conformance
struct Circle: Drawable {
    var color: Color
    var radius: Double
}

// Closure syntax
let doubled = numbers.map { $0 * 2 }

// Property wrapper
@State private var isPresented = false

Naming Conventions

// Types: PascalCase
class UserProfileViewController { }
struct NetworkRequest { }
protocol DataSource { }

// Variables/Functions: camelCase
var userName: String
func fetchUserProfile() { }

// Booleans: use is/has/should prefix
var isLoading: Bool
var hasCompletedOnboarding: Bool

Pre-Commit Checklist

• SwiftLint passes with zero warnings
• All optionals handled safely (no force unwrapping)
• Access control specified (private, internal, public)
• Memory cycles avoided (weak/unowned references)
• Unit tests cover happy and error paths

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Level 2: Implementation Guide

1. Optionals and Safety

Swift's optional system eliminates null pointer exceptions through compile-time safety.

// Safe unwrapping patterns
if let unwrapped = optionalValue {
    print(unwrapped)
}

// Multiple bindings
if let name = userName, let age = userAge, age >= 18 {
    print("\(name) is an adult")
}

// Guard for early exit
func processUser(_ user: User?) {
    guard let user = user else { return }
    print(user.name)
}

// Optional map/flatMap
let uppercasedName = userName.map { $0.uppercased() }
let userID = userIDString.flatMap { Int($0) }