Swift API Design Guidelines

extension List { public mutating func remove(at position: Index) -> Element } employees.remove(at: x)

employees.remove(x)

public mutating func removeElement(_ member: Element) -> Element? allViews.removeElement(cancelButton)

public mutating func remove(_ member: Element) -> Element? allViews.remove(cancelButton) // clearer

var string = "Hello" ❌ var greeting = "Hello" ✅

protocol ViewController { associatedtype ViewType : View ❌ } protocol ViewController { associatedtype ContentView : View ✅ }

class ProductionLine { func restock(from widgetFactory: WidgetFactory) ❌ } class ProductionLine { func restock(from supplier: WidgetFactory) ✅ }

func add(_ observer: NSObject, for keyPath: String) grid.add(self, for: graphics) ❌

func addObserver(_ observer: NSObject, forKeyPath path: String) grid.addObserver(self, forKeyPath: graphics) ✅

x.insert(y, at: z) “x, insert y at z” x.subViews(havingColor: y) “x's subviews having color y” x.capitalizingNouns() “x, capitalizing nouns”

AudioUnit.instantiate( with: description, options: [.inProcess], completionHandler: stopProgressBar)

x.makeIterator()

let foreground = Color(red: 32, green: 64, blue: 128) let newPart = factory.makeWidget(gears: 42, spindles: 14) let ref = Link(target: destination)

let rgbForeground = RGBColor(cmykForeground)

x = y.union(z) // non-mutating y.formUnion(z) // mutating

x.isEmpty line1.intersects(line2)

protocol Collection { }

protocol Equatable { } protocol ProgressReporting { }

let label = UILabel() var age = 2

var numberOfElement: Int { return 100 }

var numberOfElement: Int { (0...n).forEach { (0...n).forEach { // ... } } }

/// Time Complexity : O(n^2) var numberOfElement: Int { ... }

var utf8Bytes: [UTF8.CodeUnit] var isRepresentableAsASCII = true var userSMTPServer: SecureSMTPServer

extension Shape { /// Returns `true` if `other` is within the area of `self`; /// otherwise, `false`. func contains(_ other: Point) -> Bool { ... } /// Returns `true` if `other` is entirely within the area of `self`; /// otherwise, `false`. func contains(_ other: Shape) -> Bool { ... } /// Returns `true` if `other` is within the area of `self`; /// otherwise, `false`. func contains(_ other: LineSegment) -> Bool { ... } }

extension Collection where Element : Equatable { /// Returns `true` if `self` contains an element equal to /// `sought`; otherwise, `false`. func contains(_ sought: Element) -> Bool { ... } }

extension Database { /// Rebuilds the database's search index func index() { ... } /// Returns the `n`th row in the given table. func index(_ n: Int, inTable: TableID) -> TableRow { ... } }

extension Box { /// Returns the `Int` stored in `self`, if any, and /// `nil` otherwise. func value() -> Int? { ... } /// Returns the `String` stored in `self`, if any, and /// `nil` otherwise. func value() -> String? { ... } }

func move(from start: Point, to end: Point)

/// Return an `Array` containing the elements of `self` /// that satisfy `predicate`. func filter(_ predicate: (Element) -> Bool) -> [Generator.Element] /// Replace the given `subRange` of elements with `newElements`. mutating func replaceRange(_ subRange: Range, with newElements: [E])

/// Return an `Array` containing the elements of `self` /// that satisfy `includedInResult`. func filter(_ includedInResult: (Element) -> Bool) -> [Generator.Element] /// Replace the range of elements indicated by `r` with /// the contents of `with`. mutating func replaceRange(_ r: Range, with: [E])

extension String { /// ...description... public func compare( _ other: String, options: CompareOptions = [], range: Range? = nil, locale: Locale? = nil ) -> Ordering }

x.compare("A") x.compare("B", options: []) x.compare("C", options: [], range: nil) x.compare("D", options: [], range: nil, locale: nil)

func move(from start: Point, to end: Point)

min(x, y, z) zip(sequence1, sequence2)

Int64(someUInt32)

extension UInt32 { /// Creates an instance having the specified `value`. init(_ value: Int16) ← Widening, so no label /// Creates an instance having the lowest 32 bits of `source`. init(truncating source: UInt64) /// Creates an instance having the nearest representable /// approximation of `valueToApproximate`. init(saturating valueToApproximate: UInt64) }

x.removeBoxes(havingLength: 12)

// ❌ a.move(toX: b, y: c) a.fade(fromRed: b, green: c, blue: d) // ✅ a.moveTo(x: b, y: c) a.fadeFrom(red: b, green: c, blue: d)

view.addSubview(contentView)

view.dismiss(animated: false) let text = words.split(maxSplits: 12) let studentsByName = students.sorted(isOrderedBefore: Student.namePrecedes)

view.dismiss(false) // Don't dismiss? Dismiss a Bool? words.split(12) // Split the number 12?

/// Ensure that we hold uniquely-referenced storage for at least /// `requestedCapacity` elements. /// /// If more storage is needed, `allocate` is called with /// `byteCount` equal to the number of maximally-aligned /// bytes to allocate. /// /// - Returns: /// - reallocated: `true` if a new block of memory /// was allocated; otherwise, `false`. /// - capacityChanged: `true` if `capacity` was updated; /// otherwise, `false`. mutating func ensureUniqueStorage( minimumCapacity requestedCapacity: Int, allocate: (_ byteCount: Int) -> UnsafePointer<Void> ) -> (reallocated: Bool, capacityChanged: Bool)

let ensureStorage = ensureUniqueStorage() ensureStorage.reallocated ensureStorage.capacityChanged

struct Array { /// Inserts `newElement` at `self.endIndex`. public mutating func append(_ newElement: Element) /// Inserts the contents of `newElements`, in order, at /// `self.endIndex`. public mutating func append(_ newElements: S) where S.Generator.Element == Element }

var values: [Any] = [1, "a"] values.append([2, 3, 4]) // [1, "a", [2, 3, 4]] or [1, "a", 2, 3, 4]?😢

struct Array { /// Inserts `newElement` at `self.endIndex`. public mutating func append(_ newElement: Element) /// Inserts the contents of `newElements`, in order, at /// `self.endIndex`. public mutating func append(contentsOf newElements: S) where S.Generator.Element == Element }