[2026-04-28] Rename apple-browsers rules .mdc → .md for Obsidian compatibility
This commit is contained in:
Alexey Martemyanov
@@ -0,0 +1,975 @@
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---
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source: ~/DuckDuckGo/apple-browsers.git/main/.cursor/rules/code-style.mdc
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confidence: 0.9
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namespace: work
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last_synced: 2026-04-28
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alwaysApply: true
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---
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# Swift Code Style Guide
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*This style guide is based on the [official iOS style guide](iOS/styleguide/STYLEGUIDE.md) and incorporates DuckDuckGo-specific patterns and requirements.*
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## Correctness
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**Strive to make your code compile without warnings.** This rule informs many style decisions such as using `#selector` types instead of string literals.
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## SwiftLint
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We use [SwiftLint](https://github.com/realm/SwiftLint) for enforcing Swift style and conventions. See the [SwiftLint configuration](.swiftlint.yml) for specific rules.
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**Key SwiftLint settings**:
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- Line length: 150 characters (not the default 100)
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- Force cast/try: warnings (not errors for pragmatic development)
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- Identifier naming: flexible for single-letter variables in closures
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## Naming Conventions
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Follow the [Swift API Design Guidelines](https://swift.org/documentation/api-design-guidelines/) with these key principles:
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### Core Principles
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- **Clarity at the call site** over brevity
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- **Use camelCase** (not snake_case)
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- **UpperCamelCase** for types and protocols
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- **lowerCamelCase** for everything else
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- **Include all needed words** while omitting needless words
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- **Use names based on roles**, not types
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### Type Names
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```swift
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// ✅ CORRECT: Descriptive, UpperCamelCase
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class UserAuthenticationManager { }
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struct BookmarkItem { }
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enum NavigationState { }
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protocol DataSourceProtocol { }
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// ❌ INCORRECT: Too generic
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class Manager { }
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struct Data { }
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```
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### Variable and Function Names
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```swift
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// ✅ CORRECT: Descriptive lowerCamelCase
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let maximumRetryCount = 3
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var isLoading = false
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func fetchUserData() { }
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// Boolean properties should read like assertions
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var isEnabled: Bool
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var hasCompleted: Bool
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var canDelete: Bool
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// ❌ INCORRECT: Abbreviations and unclear names
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let usrMgr = UserManager()
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func calcTotal() { }
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```
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### Protocol Naming
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```swift
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// ✅ CORRECT: Capability protocols end in -able, -ible, -ing
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protocol Loadable { }
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protocol Refreshable { }
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protocol UserAuthenticating { }
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// ✅ CORRECT: Type protocols are nouns
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protocol DataSource { }
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protocol Delegate { }
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```
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### Method Naming Patterns
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```swift
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// ✅ CORRECT: Method naming patterns
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// Factory methods begin with "make"
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func makeLocationManager() -> CLLocationManager
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// Verb methods follow -ed, -ing rule for non-mutating
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func sorted() -> [Element] // non-mutating
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func sort() // mutating
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// Boolean methods read like assertions
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func canDelete() -> Bool
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func hasCompleted() -> Bool
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```
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### Delegate Methods
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When creating custom delegate methods, the **unnamed first parameter should be the delegate source**:
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```swift
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// ✅ CORRECT: Delegate pattern
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func namePickerView(_ namePickerView: NamePickerView, didSelectName name: String)
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func namePickerViewShouldReload(_ namePickerView: NamePickerView) -> Bool
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// ❌ INCORRECT: Missing source parameter
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func didSelectName(namePicker: NamePickerViewController, name: String)
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func namePickerShouldReload() -> Bool
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```
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### Use Type Inferred Context
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Use compiler inferred context to write shorter, clear code:
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```swift
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// ✅ CORRECT: Type inferred context
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let selector = #selector(viewDidLoad)
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view.backgroundColor = .red
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let toView = context.view(forKey: .to)
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let view = UIView(frame: .zero)
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// ❌ INCORRECT: Redundant type information
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let selector = #selector(ViewController.viewDidLoad)
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view.backgroundColor = UIColor.red
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let toView = context.view(forKey: UITransitionContextViewKey.to)
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let view = UIView(frame: CGRect.zero)
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```
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### Generics
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Generic type parameters should be **descriptive, UpperCamelCase names**:
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```swift
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// ✅ CORRECT: Descriptive generic names
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struct Stack<Element> { ... }
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func write<Target: OutputStream>(to target: inout Target)
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func swap<T>(_ a: inout T, _ b: inout T) // T is acceptable when no meaningful relationship
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// ❌ INCORRECT: Non-descriptive or wrong case
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struct Stack<T> { ... }
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func write<target: OutputStream>(to target: inout target)
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```
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### Language
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Use **US English spelling** to match Apple's API:
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```swift
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// ✅ CORRECT: US English
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let color = "red"
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// ❌ INCORRECT: British English
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let colour = "red"
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```
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## Code Organization
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### File Structure
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```swift
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// 1. Import statements (minimal - only what's needed)
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import UIKit
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import Combine
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// 2. Protocol definitions
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protocol FeatureDelegate: AnyObject {
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func featureDidUpdate()
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}
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// 3. Main type declaration
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class FeatureViewController: UIViewController {
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// Properties first
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private let viewModel: FeatureViewModel
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// Lifecycle methods
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override func viewDidLoad() {
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super.viewDidLoad()
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setupUI()
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}
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// Private methods
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private func setupUI() { }
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}
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// 4. Extensions for protocol conformance
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// MARK: - UITableViewDataSource
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extension FeatureViewController: UITableViewDataSource {
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// Protocol methods
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}
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```
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### Protocol Conformance
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**Prefer separate extensions** for protocol conformance to keep related methods grouped:
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```swift
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// ✅ CORRECT: Separate extensions
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class MyViewController: UIViewController {
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// class implementation
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}
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// MARK: - UITableViewDataSource
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extension MyViewController: UITableViewDataSource {
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// table view data source methods
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}
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// MARK: - UIScrollViewDelegate
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extension MyViewController: UIScrollViewDelegate {
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// scroll view delegate methods
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}
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// ❌ INCORRECT: All in main class declaration
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class MyViewController: UIViewController, UITableViewDataSource, UIScrollViewDelegate {
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// all methods mixed together
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}
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```
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### Minimal Imports
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**Import only the modules a source file requires**:
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```swift
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// ✅ CORRECT: Minimal imports
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import UIKit
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var view: UIView
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var deviceModels: [String]
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// ✅ CORRECT: Foundation when UIKit not needed
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import Foundation
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var deviceModels: [String]
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// ❌ INCORRECT: Unnecessary imports
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import UIKit
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import Foundation // UIKit already includes Foundation
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var view: UIView
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var deviceModels: [String]
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```
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### Remove Unused Code
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**Remove unused (dead) code**, including Xcode template code:
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```swift
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// ✅ CORRECT: Keep only implemented methods
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override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
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return Database.contacts.count
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}
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// ❌ INCORRECT: Template code and unused methods
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override func didReceiveMemoryWarning() {
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super.didReceiveMemoryWarning()
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// Dispose of any resources that can be recreated.
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}
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override func numberOfSections(in tableView: UITableView) -> Int {
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// #warning Incomplete implementation, return the number of sections
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return 1
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}
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```
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## Formatting and Style
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### Line Breaks and Length
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- **Line margin: 150 characters** (not the default 100)
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- **Long lines should be wrapped** at around 150 characters
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- **Avoid trailing whitespace** at ends of lines
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- **Add single newline** at end of each file
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### Spacing
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- **Indent using 4 spaces** rather than tabs
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- **Method braces open on same line**, close on new line
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- **One blank line between methods**
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- **No blank lines after opening brace or before closing brace**
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```swift
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// ✅ CORRECT: Spacing and braces
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if user.isHappy {
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// Do something
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} else {
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// Do something else
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}
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// ❌ INCORRECT: Wrong brace placement
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if user.isHappy
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{
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// Do something
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}
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else {
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// Do something else
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}
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```
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### Colons
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**Colons have no space on left, one space on right**. Exceptions: ternary operator `? :`, empty dictionary `[:]`, `#selector` syntax:
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```swift
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// ✅ CORRECT: Colon spacing
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class TestDatabase: Database {
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var data: [String: CGFloat] = ["A": 1.2, "B": 3.2]
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}
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// ❌ INCORRECT: Wrong colon spacing
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class TestDatabase : Database {
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var data :[String:CGFloat] = ["A" : 1.2, "B":3.2]
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}
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```
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### Function Parameters
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**Closing parentheses should not appear on line by themselves**:
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```swift
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// ✅ CORRECT: Closing parenthesis placement
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let user = try await getUser(
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for: userID,
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on: connection)
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// ❌ INCORRECT: Closing parenthesis on own line
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let user = try await getUser(
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for: userID,
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on: connection
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)
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```
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## Function Declarations
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### Short Functions
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**Keep short function declarations on one line**:
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```swift
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// ✅ CORRECT: Short function on one line
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func reticulateSplines(spline: [Double]) -> Bool {
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// implementation
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}
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```
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### Long Function Signatures
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**For functions with long signatures, put each parameter on new line**:
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```swift
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// ✅ CORRECT: Long signature formatting
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func reticulateSplines(spline: [Double],
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adjustmentFactor: Double,
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translateConstant: Int,
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comment: String) -> Bool {
|
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// implementation
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}
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```
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### Return Types
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**Use `Void` for closure/function outputs, `()` for inputs**:
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```swift
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// ✅ CORRECT: Return type formatting
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func updateConstraints() -> Void {
|
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// implementation
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}
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typealias CompletionHandler = (result) -> Void
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|
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// ❌ INCORRECT: Wrong return type syntax
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func updateConstraints() -> () {
|
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// implementation
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}
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typealias CompletionHandler = (result) -> ()
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```
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## Function Calls
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**Mirror function declaration style at call sites**:
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|
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```swift
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// ✅ CORRECT: Single line when it fits
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let success = reticulateSplines(splines)
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// ✅ CORRECT: Multi-line when wrapped
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let success = reticulateSplines(
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spline: splines,
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adjustmentFactor: 1.3,
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translateConstant: 2,
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comment: "normalize the display")
|
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```
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## Closure Expressions
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### Trailing Closure Syntax
|
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**Use trailing closure syntax only for single closure at end**:
|
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|
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```swift
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// ✅ CORRECT: Trailing closure usage
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UIView.animate(withDuration: 1.0) {
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self.myView.alpha = 0
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}
|
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|
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UIView.animate(withDuration: 1.0, animations: {
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self.myView.alpha = 0
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}, completion: { finished in
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self.myView.removeFromSuperview()
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||||
})
|
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|
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// ❌ INCORRECT: Trailing closure with multiple closures
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UIView.animate(withDuration: 1.0, animations: {
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self.myView.alpha = 0
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}) { f in
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self.myView.removeFromSuperview()
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}
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```
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|
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### Single-Expression Closures
|
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**Use implicit returns for single-expression closures**:
|
||||
|
||||
```swift
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// ✅ CORRECT: Implicit return
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attendeeList.sort { a, b in
|
||||
a > b
|
||||
}
|
||||
```
|
||||
|
||||
### Chained Methods
|
||||
**Format chained methods for clarity**:
|
||||
|
||||
```swift
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||||
// ✅ CORRECT: Chained methods - compact when clear
|
||||
let value = numbers.map { $0 * 2 }.filter { $0 % 3 == 0 }.index(of: 90)
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|
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// ✅ CORRECT: Chained methods - multi-line when complex
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let value = numbers
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.map { $0 * 2 }
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.filter { $0 > 50 }
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.map { $0 + 10 }
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```
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|
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## Types and Constants
|
||||
|
||||
### Native Types
|
||||
**Always use Swift's native types** when available:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Native Swift types
|
||||
let width = 120.0 // Double
|
||||
let widthString = "\(width)" // String
|
||||
|
||||
// ❌ INCORRECT: Objective-C types
|
||||
let width: NSNumber = 120.0 // NSNumber
|
||||
let widthString: NSString = width.stringValue // NSString
|
||||
```
|
||||
|
||||
### Constants vs Variables
|
||||
**Use `let` by default, change to `var` only when compiler complains**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Type properties for constants
|
||||
enum Math {
|
||||
static let e = 2.718281828459045235360287
|
||||
static let root2 = 1.41421356237309504880168872
|
||||
}
|
||||
|
||||
let hypotenuse = side * Math.root2
|
||||
|
||||
// ❌ INCORRECT: Global constants
|
||||
let e = 2.718281828459045235360287 // pollutes global namespace
|
||||
let root2 = 1.41421356237309504880168872
|
||||
```
|
||||
|
||||
### Type Inference
|
||||
**Prefer compact code and let compiler infer types**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Type inference
|
||||
let message = "Click the button"
|
||||
let currentBounds = computeViewBounds()
|
||||
var names = ["Mic", "Sam", "Christine"]
|
||||
let maximumWidth: CGFloat = 106.5 // Specify when needed
|
||||
|
||||
// ❌ INCORRECT: Unnecessary type annotations
|
||||
let message: String = "Click the button"
|
||||
let currentBounds: CGRect = computeViewBounds()
|
||||
```
|
||||
|
||||
### Empty Collections
|
||||
**Use type annotation for empty arrays and dictionaries**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Type annotation for empty collections
|
||||
var names: [String] = []
|
||||
var lookup: [String: Int] = [:]
|
||||
|
||||
// ❌ INCORRECT: Constructor syntax
|
||||
var names = [String]()
|
||||
var lookup = [String: Int]()
|
||||
```
|
||||
|
||||
### Syntactic Sugar
|
||||
**Prefer shortcut type declarations**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Syntactic sugar
|
||||
var deviceModels: [String]
|
||||
var employees: [Int: String]
|
||||
var faxNumber: Int?
|
||||
|
||||
// ❌ INCORRECT: Full generics syntax
|
||||
var deviceModels: Array<String>
|
||||
var employees: Dictionary<Int, String>
|
||||
var faxNumber: Optional<Int>
|
||||
```
|
||||
|
||||
## Optionals
|
||||
|
||||
### Optional Declarations
|
||||
**Use `?` for optional types, `!` only when you know initialization timing**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Optional usage
|
||||
var subview: UIView?
|
||||
var volume: Double?
|
||||
|
||||
// Use ! only for outlets that initialize in viewDidLoad
|
||||
@IBOutlet weak var tableView: UITableView!
|
||||
```
|
||||
|
||||
### Optional Binding
|
||||
**Shadow original names in optional binding**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Shadow original name
|
||||
if let subview = subview, let volume = volume {
|
||||
// do something with unwrapped subview and volume
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Different names for unwrapped values
|
||||
if let unwrappedSubview = optionalSubview {
|
||||
if let realVolume = volume {
|
||||
// do something with unwrappedSubview and realVolume
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Optional Chaining vs Binding
|
||||
**Use optional chaining for single access, binding for multiple operations**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Optional chaining for single access
|
||||
textContainer?.textLabel?.setNeedsDisplay()
|
||||
|
||||
// ✅ CORRECT: Optional binding for multiple operations
|
||||
if let textContainer = textContainer {
|
||||
// do many things with textContainer
|
||||
}
|
||||
```
|
||||
|
||||
## Memory Management
|
||||
|
||||
### Reference Cycles
|
||||
**Prevent reference cycles with `weak` and `unowned` references.**
|
||||
|
||||
**Example:** See [memory-management.swift](code-style/memory-management.swift)
|
||||
|
||||
### Lazy Initialization
|
||||
**Use lazy initialization for fine-grained control**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Lazy initialization
|
||||
lazy var locationManager = makeLocationManager()
|
||||
|
||||
private func makeLocationManager() -> CLLocationManager {
|
||||
let manager = CLLocationManager()
|
||||
manager.desiredAccuracy = kCLLocationAccuracyBest
|
||||
manager.delegate = self
|
||||
manager.requestAlwaysAuthorization()
|
||||
return manager
|
||||
}
|
||||
```
|
||||
|
||||
## Access Control
|
||||
|
||||
### Access Control Order
|
||||
**Access control comes first, except for `static` and attributes**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Access control ordering
|
||||
private let message = "Great Scott!"
|
||||
|
||||
class TimeMachine {
|
||||
private dynamic lazy var fluxCapacitor = FluxCapacitor()
|
||||
@IBAction private func activate() { }
|
||||
static private let timeConstant = 88.0
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Wrong ordering
|
||||
fileprivate let message = "Great Scott!"
|
||||
|
||||
class TimeMachine {
|
||||
lazy dynamic private var fluxCapacitor = FluxCapacitor()
|
||||
}
|
||||
```
|
||||
|
||||
### Private vs Fileprivate
|
||||
**Prefer `private` to `fileprivate`**; use `fileprivate` only when compiler requires it.
|
||||
|
||||
## Control Flow
|
||||
|
||||
### Loop Style
|
||||
**Prefer `for-in` style over `while-condition-increment`**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: for-in style
|
||||
for _ in 0..<3 {
|
||||
print("Hello three times")
|
||||
}
|
||||
|
||||
for (index, person) in attendeeList.enumerated() {
|
||||
print("\(person) is at position #\(index)")
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: while style
|
||||
var i = 0
|
||||
while i < 3 {
|
||||
print("Hello three times")
|
||||
i += 1
|
||||
}
|
||||
```
|
||||
|
||||
### Ternary Operator
|
||||
**Use ternary operator only when it increases clarity**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Simple ternary usage
|
||||
let value = 5
|
||||
result = value != 0 ? x : y
|
||||
|
||||
let isHorizontal = true
|
||||
result = isHorizontal ? x : y
|
||||
|
||||
// ❌ INCORRECT: Complex nested ternary
|
||||
result = a > b ? x = c > d ? c : d : y
|
||||
```
|
||||
|
||||
### Golden Path
|
||||
**Use the "golden path" pattern - don't nest `if` statements**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Golden path with guard
|
||||
func computeFFT(context: Context?, inputData: InputData?) throws -> Frequencies {
|
||||
guard let context = context else {
|
||||
throw FFTError.noContext
|
||||
}
|
||||
guard let inputData = inputData else {
|
||||
throw FFTError.noInputData
|
||||
}
|
||||
|
||||
// use context and input to compute the frequencies
|
||||
return frequencies
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Nested if statements
|
||||
func computeFFT(context: Context?, inputData: InputData?) throws -> Frequencies {
|
||||
if let context = context {
|
||||
if let inputData = inputData {
|
||||
// use context and input to compute the frequencies
|
||||
return frequencies
|
||||
} else {
|
||||
throw FFTError.noInputData
|
||||
}
|
||||
} else {
|
||||
throw FFTError.noContext
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Compound Guard Statements
|
||||
**Use compound guard for multiple optionals**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Compound guard
|
||||
guard
|
||||
let number1 = number1,
|
||||
let number2 = number2,
|
||||
let number3 = number3
|
||||
else {
|
||||
fatalError("impossible")
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Nested optional binding
|
||||
if let number1 = number1 {
|
||||
if let number2 = number2 {
|
||||
if let number3 = number3 {
|
||||
// do something with numbers
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## Class and Struct Definitions
|
||||
|
||||
### Example Well-Styled Class
|
||||
```swift
|
||||
final class Circle: Shape {
|
||||
var x: Int, y: Int
|
||||
var radius: Double
|
||||
var diameter: Double {
|
||||
get {
|
||||
radius * 2
|
||||
}
|
||||
set {
|
||||
radius = newValue / 2
|
||||
}
|
||||
}
|
||||
|
||||
init(x: Int, y: Int, radius: Double) {
|
||||
self.x = x
|
||||
self.y = y
|
||||
self.radius = radius
|
||||
}
|
||||
|
||||
convenience init(x: Int, y: Int, diameter: Double) {
|
||||
self.init(x: x, y: y, radius: diameter / 2)
|
||||
}
|
||||
|
||||
override func area() -> Double {
|
||||
Double.pi * radius * radius
|
||||
}
|
||||
}
|
||||
|
||||
extension Circle: CustomStringConvertible {
|
||||
var description: String {
|
||||
"center = \(centerString) area = \(area())"
|
||||
}
|
||||
|
||||
private var centerString: String {
|
||||
"(\(x),\(y))"
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Use of Self
|
||||
**Avoid using `self` unless required by compiler**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Self only when required
|
||||
class PhotoViewController: UIViewController {
|
||||
var image: UIImage
|
||||
|
||||
init(image: UIImage) {
|
||||
self.image = image // Required to disambiguate
|
||||
super.init(nibName: nil, bundle: nil)
|
||||
}
|
||||
|
||||
func setupImageView() {
|
||||
imageView.image = image // self not needed
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Computed Properties
|
||||
**Omit get clause for read-only computed properties**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Implicit get for read-only
|
||||
var diameter: Double {
|
||||
radius * 2
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Unnecessary get clause
|
||||
var diameter: Double {
|
||||
get {
|
||||
return radius * 2
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
### Final
|
||||
**Use `final` when inheritance is not intended**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Final for utility classes
|
||||
final class Box<T> {
|
||||
let value: T
|
||||
init(_ value: T) {
|
||||
self.value = value
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## DuckDuckGo-Specific Patterns
|
||||
|
||||
### Design System Integration (MANDATORY)
|
||||
|
||||
**ALWAYS use DesignResourcesKit** for colors, typography, and icons.
|
||||
|
||||
**Example:** See [design-system-integration.swift](code-style/design-system-integration.swift)
|
||||
|
||||
### Dependency Injection Pattern
|
||||
**Use AppDependencyProvider for dependency injection.**
|
||||
|
||||
**Example:** See [dependency-injection.swift](code-style/dependency-injection.swift)
|
||||
|
||||
### Async/Await Patterns
|
||||
**Example:** See [async-await-pattern.swift](code-style/async-await-pattern.swift)
|
||||
|
||||
### Property Wrappers
|
||||
**Example:** See [property-wrappers.swift](code-style/property-wrappers.swift)
|
||||
|
||||
## Comments and Documentation
|
||||
|
||||
### When to Comment
|
||||
**Use comments to explain WHY, not WHAT**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Explains why
|
||||
// We delay the animation to avoid conflicting with the previous transition
|
||||
DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
|
||||
self.animateTransition()
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Explains what (obvious from code)
|
||||
// Set the background color to red
|
||||
view.backgroundColor = .red
|
||||
```
|
||||
|
||||
### Comment Style
|
||||
**Prefer double/triple-slash over C-style comments**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Swift-style comments
|
||||
// This is a comment
|
||||
/// This is a documentation comment
|
||||
|
||||
// ❌ INCORRECT: C-style comments
|
||||
/* This is a comment */
|
||||
```
|
||||
|
||||
## String Literals
|
||||
|
||||
### Multi-line Strings
|
||||
**Use multi-line string syntax for long strings**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Multi-line string formatting
|
||||
let message = """
|
||||
You cannot charge the flux \
|
||||
capacitor with a 9V battery.
|
||||
You must use a super-charger \
|
||||
which costs 10 credits. You currently \
|
||||
have \(credits) credits available.
|
||||
"""
|
||||
|
||||
// ❌ INCORRECT: Concatenation or inline text
|
||||
let message = """You cannot charge the flux \
|
||||
capacitor with a 9V battery.
|
||||
You must use a super-charger \
|
||||
which costs 10 credits. You currently \
|
||||
have \(credits) credits available.
|
||||
"""
|
||||
```
|
||||
|
||||
## Prohibited Patterns
|
||||
|
||||
### No Emoji
|
||||
**Do not use emoji in code** - it creates unnecessary friction:
|
||||
|
||||
```swift
|
||||
// ❌ FORBIDDEN: Emoji in code
|
||||
let isHappy = true 😀
|
||||
func celebrate() 🎉 { }
|
||||
|
||||
// ✅ CORRECT: Clear, text-based names
|
||||
let isHappy = true
|
||||
func celebrate() { }
|
||||
```
|
||||
|
||||
### No Color/Image Literals
|
||||
**Do not use `#colorLiteral` or `#imageLiteral`** - they're hard to read and maintain:
|
||||
|
||||
```swift
|
||||
// ❌ FORBIDDEN: Literals
|
||||
let color = #colorLiteral(red: 1, green: 0, blue: 0, alpha: 1)
|
||||
let image = #imageLiteral(resourceName: "icon")
|
||||
|
||||
// ✅ CORRECT: Explicit constructors (but prefer DesignResourcesKit)
|
||||
let color = UIColor(red: 1, green: 0, blue: 0, alpha: 1)
|
||||
let image = UIImage(named: "icon")
|
||||
|
||||
// ✅ BEST: DesignResourcesKit
|
||||
let color = UIColor(designSystemColor: .accent)
|
||||
let image = DesignSystemImages.Color.Size24.bookmark
|
||||
```
|
||||
|
||||
### No Parentheses Around Conditionals
|
||||
**Don't use unnecessary parentheses**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: No parentheses needed
|
||||
if name == "Hello" {
|
||||
print("World")
|
||||
}
|
||||
|
||||
// ❌ INCORRECT: Unnecessary parentheses
|
||||
if (name == "Hello") {
|
||||
print("World")
|
||||
}
|
||||
```
|
||||
|
||||
### No Semicolons
|
||||
**Swift doesn't require semicolons** - don't use them:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: No semicolons
|
||||
let swift = "not a scripting language"
|
||||
|
||||
// ❌ INCORRECT: Unnecessary semicolons
|
||||
let swift = "not a scripting language";
|
||||
```
|
||||
|
||||
## Error Handling and Assertions
|
||||
|
||||
### Fatal Errors
|
||||
**Use `fatalError()` when app reaches unrecoverable state**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Fatal error for impossible states
|
||||
guard let viewController = storyboard.instantiateViewController(withIdentifier: "Main") as? MainViewController else {
|
||||
fatalError("Failed to instantiate MainViewController from storyboard")
|
||||
}
|
||||
```
|
||||
|
||||
### Assertions
|
||||
**Use `assert()` and `assertionFailure()` for recoverable but unexpected states**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Assert for development debugging
|
||||
func processItems(_ items: [Item]) {
|
||||
assert(!items.isEmpty, "Items array should not be empty")
|
||||
|
||||
// Handle empty array gracefully in release builds
|
||||
guard !items.isEmpty else { return }
|
||||
|
||||
// Process items...
|
||||
}
|
||||
```
|
||||
|
||||
## Logging
|
||||
|
||||
**Use unified logging system** for all logging.
|
||||
|
||||
**Example:** See [logging-pattern.swift](code-style/logging-pattern.swift)
|
||||
|
||||
**See [Logging Guidelines](logging-guidelines.md) for comprehensive logging patterns.**
|
||||
|
||||
## Unit Test Naming
|
||||
|
||||
**Use "when/then" convention for test names**:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: When/then test naming
|
||||
func testWhenUrlIsNotATrackerThenMatchesIsFalse() { }
|
||||
func testWhenUserTapsBookmarkButtonThenBookmarkIsAdded() { }
|
||||
func testWhenNetworkFailsThenErrorIsDisplayed() { }
|
||||
|
||||
// ❌ INCORRECT: Unclear test names
|
||||
func testBookmarks() { }
|
||||
func testNetworking() { }
|
||||
```
|
||||
|
||||
## Functions vs Methods
|
||||
|
||||
**Prefer methods over free functions** for discoverability:
|
||||
|
||||
```swift
|
||||
// ✅ CORRECT: Methods are easily discoverable
|
||||
let sorted = items.mergeSorted()
|
||||
rocket.launch()
|
||||
|
||||
// ❌ INCORRECT: Free functions are hard to discover
|
||||
let sorted = mergeSort(items)
|
||||
launch(&rocket)
|
||||
|
||||
// ✅ ACCEPTABLE: Free functions that feel natural
|
||||
let tuples = zip(a, b)
|
||||
let value = max(x, y, z)
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
**Remember**: This style guide ensures consistency across the DuckDuckGo browser codebase. When in doubt, prioritize clarity and follow the patterns established in existing code.
|
||||
Reference in New Issue
Block a user