code-style

Swift Code Style Guide

This style guide is based on the official iOS style guide and incorporates DuckDuckGo-specific patterns and requirements.

Correctness

Strive to make your code compile without warnings. This rule informs many style decisions such as using #selector types instead of string literals.

SwiftLint

We use SwiftLint for enforcing Swift style and conventions. See the SwiftLint configuration for specific rules.

Key SwiftLint settings:

• Line length: 150 characters (not the default 100)
• Force cast/try: warnings (not errors for pragmatic development)
• Identifier naming: flexible for single-letter variables in closures

Naming Conventions

Follow the Swift API Design Guidelines with these key principles:

Core Principles

• Clarity at the call site over brevity
• Use camelCase (not snake_case)
• UpperCamelCase for types and protocols
• lowerCamelCase for everything else
• Include all needed words while omitting needless words
• Use names based on roles, not types

Type Names

// ✅ CORRECT: Descriptive, UpperCamelCase
class UserAuthenticationManager { }
struct BookmarkItem { }
enum NavigationState { }
protocol DataSourceProtocol { }

// ❌ INCORRECT: Too generic
class Manager { }
struct Data { }

Variable and Function Names

// ✅ CORRECT: Descriptive lowerCamelCase
let maximumRetryCount = 3
var isLoading = false
func fetchUserData() { }

// Boolean properties should read like assertions
var isEnabled: Bool
var hasCompleted: Bool
var canDelete: Bool

// ❌ INCORRECT: Abbreviations and unclear names
let usrMgr = UserManager()
func calcTotal() { }

Protocol Naming

// ✅ CORRECT: Capability protocols end in -able, -ible, -ing
protocol Loadable { }
protocol Refreshable { }
protocol UserAuthenticating { }

// ✅ CORRECT: Type protocols are nouns
protocol DataSource { }
protocol Delegate { }