import Swift
import FoundationA short cheat-sheet with Xcode 6 Playground (Design-Patterns.playground.zip).
👷 Project maintained by: @nsmeme (Oktawian Chojnacki)
In software engineering, creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. The basic form of object creation could result in design problems or added complexity to the design. Creational design patterns solve this problem by somehow controlling this object creation.
Source: wikipedia.org
##💍 Singleton
class SingletonClass {
class var shared : SingletonClass {
struct Static {
static let instance : SingletonClass = SingletonClass()
}
return Static.instance
}
}Usage:
let instance = SingletonClass.shared##👷 Builder
protocol ThreeDimensions {
var x: Double? {get}
var y: Double? {get}
var z: Double? {get}
}
class Point : ThreeDimensions {
var x: Double?
var y: Double?
var z: Double?
typealias PointBuilderClosure = (Point) -> ()
init(buildClosure: PointBuilderClosure) {
buildClosure(self)
}
}Usage:
let fancyPoint = Point { point in
point.x = 0.1
point.y = 0.2
point.z = 0.3
}
fancyPoint.x
fancyPoint.y
fancyPoint.zShorter but oh-so-ugly alternative:
let uglierPoint = Point {
$0.x = 0.1
$0.y = 0.2
$0.z = 0.3
}##🌰 Abstract Factory
// Protocols.
protocol Decimal {
func stringValue() -> String
}
protocol NumberFactoryProtocol {
func numberFromString(string : String) -> Decimal
}
// Number implementations.
struct NextStepNumber : Decimal {
private var nextStepNumber : NSNumber
func stringValue() -> String { return nextStepNumber.stringValue }
}
struct SwiftNumber : Decimal {
private var swiftInt : Int
func stringValue() -> String { return "\(swiftInt)" }
}
// Factories.
class NextStepNumberFactory : NumberFactoryProtocol {
func numberFromString(string : String) -> Decimal {
return NextStepNumber(nextStepNumber:NSNumber(longLong:(string as NSString).longLongValue))
}
}
class SwiftNumberFactory : NumberFactoryProtocol {
func numberFromString(string : String) -> Decimal {
return SwiftNumber(swiftInt:(string as NSString).integerValue)
}
}
// Abstract factory.
enum NumberType {
case NextStep, Swift
}
class NumberAbstractFactory {
class func numberFactoryType(type : NumberType) -> NumberFactoryProtocol {
switch type {
case .NextStep:
return NextStepNumberFactory()
case .Swift:
return SwiftNumberFactory()
}
}
}Usage:
let factoryOne = NumberAbstractFactory.numberFactoryType(.NextStep)
let numberOne = factoryOne.numberFromString("1")
numberOne.stringValue()
let factoryTwo = NumberAbstractFactory.numberFactoryType(.Swift)
let numberTwo = factoryTwo.numberFromString("2")
numberTwo.stringValue()##🃏 Prototype
class ThieveryCorporationPersonDisplay {
var name: String?
let font: String
init(font: String) {
self.font = font
}
func clone() -> ThieveryCorporationPersonDisplay {
return ThieveryCorporationPersonDisplay(font:self.font)
}
}Usage:
let Prototype = ThieveryCorporationPersonDisplay(font:"Ubuntu")
let Philippe = Prototype.clone()
Philippe.name = "Philippe"
let Christoph = Prototype.clone()
Christoph.name = "Christoph"
let Eduardo = Prototype.clone()
Eduardo.name = "Eduardo"##🏭 Factory Method
protocol Currency {
func symbol() -> String
func code() -> String
}
class Euro : Currency {
func symbol() -> String {
return "€"
}
func code() -> String {
return "EUR"
}
}
class UnitedStatesDolar : Currency {
func symbol() -> String {
return "$"
}
func code() -> String {
return "USD"
}
}
enum Country {
case UnitedStates, Spain, France, UK
}
class CurrencyFactory {
class func currencyForCountry(country:Country) -> Currency? {
switch country {
case .Spain, .France :
return Euro()
case .UnitedStates :
return UnitedStatesDolar()
default:
return nil
}
}
}Usage:
let noCurrencyCode = "No Currency Code Available"
CurrencyFactory.currencyForCountry(.Spain)?.code() ?? noCurrencyCode
CurrencyFactory.currencyForCountry(.UnitedStates)?.code() ?? noCurrencyCode
CurrencyFactory.currencyForCountry(.France)?.code() ?? noCurrencyCode
CurrencyFactory.currencyForCountry(.UK)?.code() ?? noCurrencyCode#Structural
In software engineering, structural design patterns are design patterns that ease the design by identifying a simple way to realize relationships between entities.
Source: wikipedia.org
##🌿 Composite
/**
* Component
*/
protocol Shape {
func draw(fillColor: String)
}
/**
* Leafs
*/
class Square : Shape {
func draw(fillColor: String) {
print("Drawing a Square with color \(fillColor)")
}
}
class Circle : Shape {
func draw(fillColor: String) {
print("Drawing a circle with color \(fillColor)")
}
}
/**
* Composite
*/
class Whiteboard : Shape {
lazy var shapes = [Shape]()
init(_ shapes:Shape...) {
self.shapes = shapes
}
func draw(fillColor:String) {
for shape in self.shapes {
shape.draw(fillColor)
}
}
}Usage:
var whiteboard = Whiteboard(Circle(), Square())
whiteboard.draw("Red")##🎁 Façade
class Eternal {
class func setObject(value: AnyObject!, forKey defaultName: String!) {
let defaults:NSUserDefaults = NSUserDefaults.standardUserDefaults()
defaults.setObject(value, forKey:defaultName)
defaults.synchronize()
}
class func objectForKey(defaultName: String!) -> AnyObject! {
let defaults:NSUserDefaults = NSUserDefaults.standardUserDefaults()
return defaults.objectForKey(defaultName)
}
}Usage:
Eternal.setObject("Disconnect me. I’d rather be nothing", forKey:"Bishop")
Eternal.objectForKey("Bishop")##🔌 Adapter
// WARNING: This example uses Point class from Builder pattern!
class PointConverter {
class func convert(#point:Point, base:Double, negative:Bool) -> Point {
var pointConverted = Point{
if let x = point.x { $0.x = x * base * (negative ? -1.0 : 1.0) }
if let y = point.y { $0.y = y * base * (negative ? -1.0 : 1.0) }
if let z = point.z { $0.z = z * base * (negative ? -1.0 : 1.0) }
}
return pointConverted
}
}
extension PointConverter{
class func convert(#x:Double!, y:Double!, z:Double!, base:Double!, negative:Bool!) -> (x:Double!,y:Double!,z:Double!) {
var point = Point{ $0.x = x; $0.y = y; $0.z = z }
var pointCalculated = self.convert(point:point, base:base, negative:negative)
return (pointCalculated.x!,pointCalculated.y!,pointCalculated.z!)
}
}Usage:
var tuple = PointConverter.convert(x:1.1, y:2.2, z:3.3, base:2.0, negative:true)
tuple.x
tuple.y
tuple.z##🌉 Bridge
protocol Switch {
var appliance: Appliance {get set}
func turnOn()
}
protocol Appliance {
func run()
}
class RemoteControl: Switch {
var appliance: Appliance
func turnOn() {
self.appliance.run()
}
init(appliance: Appliance) {
self.appliance = appliance
}
}
class TV: Appliance {
func run() {
println("tv turned on");
}
}
class VacuumCleaner: Appliance {
func run() {
println("vacuum cleaner turned on")
}
}Usage
var tvRemoteControl = RemoteControl(appliance: TV())
tvRemoteControl.turnOn()
var fancyVacuumCleanerRemoteControl = RemoteControl(appliance: VacuumCleaner())
fancyVacuumCleanerRemoteControl.turnOn()##🍧 Decorator
protocol Coffee {
func getCost() -> Double
func getIngredients() -> String
}
class SimpleCoffee: Coffee {
func getCost() -> Double {
return 1.0
}
func getIngredients() -> String {
return "Coffee"
}
}
class CoffeeDecorator: Coffee {
private let decoratedCoffee: Coffee
private let ingredientSeparator: String = ", "
required init(decoratedCoffee: Coffee) {
self.decoratedCoffee = decoratedCoffee
}
func getCost() -> Double {
return decoratedCoffee.getCost()
}
func getIngredients() -> String {
return decoratedCoffee.getIngredients()
}
}
class Milk: CoffeeDecorator {
required init(decoratedCoffee: Coffee) {
super.init(decoratedCoffee: decoratedCoffee)
}
override func getCost() -> Double {
return super.getCost() + 0.5
}
override func getIngredients() -> String {
return super.getIngredients() + ingredientSeparator + "Milk"
}
}
class WhipCoffee: CoffeeDecorator {
required init(decoratedCoffee: Coffee) {
super.init(decoratedCoffee: decoratedCoffee)
}
override func getCost() -> Double {
return super.getCost() + 0.7
}
override func getIngredients() -> String {
return super.getIngredients() + ingredientSeparator + "Whip"
}
}Usage:
var someCoffee: Coffee = SimpleCoffee()
println("Cost : \(someCoffee.getCost()); Ingredients: \(someCoffee.getIngredients())")
someCoffee = Milk(decoratedCoffee: someCoffee)
println("Cost : \(someCoffee.getCost()); Ingredients: \(someCoffee.getIngredients())")
someCoffee = WhipCoffee(decoratedCoffee: someCoffee)
println("Cost : \(someCoffee.getCost()); Ingredients: \(someCoffee.getIngredients())")##🍬 Virtual Proxy
Source:
protocol HEVSuitMedicalAid {
func administerMorphine() -> String
}
class HEVSuit : HEVSuitMedicalAid {
func administerMorphine() -> String {
return "Morphine aministered."
}
}
class HEVSuitHumanInterface : HEVSuitMedicalAid {
lazy private var physicalSuit: HEVSuit = HEVSuit()
func administerMorphine() -> String {
return physicalSuit.administerMorphine()
}
}Usage:
let humanInterface = HEVSuitHumanInterface()
humanInterface.administerMorphine()##☔ Protection Proxy
Source:
protocol DoorOperator {
func openDoors(doors: String) -> String
}
class HAL9000 : DoorOperator {
func openDoors(doors: String) -> String {
return ("HAL9000: Affirmative, Dave. I read you. Opened \(doors).")
}
}
class CurrentComputer : DoorOperator {
private var computer: HAL9000!
func authenticateWithPassword(pass: String) -> Bool {
if pass != "pass" {
return false
}
computer = HAL9000()
return true
}
func openDoors(doors: String) -> String {
if (computer == nil) {
return "Access Denied. I'm afraid I can't do that."
}
return computer.openDoors(doors)
}
}Usage:
let computer = CurrentComputer()
let doors = "Pod Bay Doors"
computer.openDoors(doors)
computer.authenticateWithPassword("pass")
computer.openDoors(doors)#Behavioral
In software engineering, behavioral design patterns are design patterns that identify common communication patterns between objects and realize these patterns. By doing so, these patterns increase flexibility in carrying out this communication.
Source: wikipedia.org
##🐝 Chain Of Responsibility
Source:
class MoneyPile {
let value: Int
var quantity: Int
var nextPile: MoneyPile?
init(value: Int, quantity: Int, nextPile: MoneyPile?) {
self.value = value
self.quantity = quantity
self.nextPile = nextPile
}
func canWithdraw(var v: Int) -> Bool {
func canTakeSomeBill(want: Int) -> Bool {
return (want / self.value) > 0
}
var q = self.quantity
while canTakeSomeBill(v) {
if (q == 0) {
break
}
v -= self.value
q -= 1
}
if v == 0 {
return true
} else if let next = self.nextPile {
return next.canWithdraw(v)
}
return false
}
}
class ATM {
private var hundred: MoneyPile
private var fifty: MoneyPile
private var twenty: MoneyPile
private var ten: MoneyPile
private var startPile: MoneyPile {
return self.hundred
}
init(hundred: MoneyPile,
fifty: MoneyPile,
twenty: MoneyPile,
ten: MoneyPile) {
self.hundred = hundred
self.fifty = fifty
self.twenty = twenty
self.ten = ten
}
func canWithdraw(value: Int) -> String {
return "Can withdraw: \(self.startPile.canWithdraw(value))"
}
}Usage:
// Create piles of money and link them together 10 < 20 < 50 < 100.
let ten = MoneyPile(value: 10, quantity: 6, nextPile: nil)
let twenty = MoneyPile(value: 20, quantity: 2, nextPile: ten)
let fifty = MoneyPile(value: 50, quantity: 2, nextPile: twenty)
let hundred = MoneyPile(value: 100, quantity: 1, nextPile: fifty)
// Build ATM.
var atm = ATM(hundred: hundred, fifty: fifty, twenty: twenty, ten: ten)
atm.canWithdraw(310) // Cannot because ATM has only 300
atm.canWithdraw(100) // Can withdraw - 1x100
atm.canWithdraw(165) // Cannot withdraw because ATM doesn't has bill with value of 5
atm.canWithdraw(30) // Can withdraw - 1x20, 2x10##👫 Command
protocol FileOperationCommand {
init(file: String)
func execute()
}
class FileMoveCommand : FileOperationCommand {
let file:String
required init(file: String) {
self.file = file
}
func execute() {
print("\(file) moved")
}
}
class FileDeleteCommand : FileOperationCommand {
let file:String
required init(file: String) {
self.file = file
}
func execute() {
print("\(file) deleted")
}
}
class FileManager {
let deleteCommand: FileOperationCommand
let moveCommand: FileOperationCommand
init(deleteCommand: FileDeleteCommand, moveCommand: FileMoveCommand) {
self.deleteCommand = deleteCommand
self.moveCommand = moveCommand
}
func delete() {
deleteCommand.execute()
}
func move() {
moveCommand.execute()
}
}Usage:
let deleteCommand = FileDeleteCommand(file: "/path/to/testfile")
let moveCommand = FileMoveCommand(file: "/path/to/testfile")
let fileManager = FileManager(deleteCommand:deleteCommand , moveCommand: moveCommand)
fileManager.delete()
fileManager.move()##🚧 Iterator ##🚧 Mediator ##🚧 Memento ##👓 Observer
class StepCounter {
var totalSteps: Int = 0 {
willSet(newTotalSteps) {
println("About to set totalSteps to \(newTotalSteps)")
}
didSet {
if totalSteps > oldValue {
println("Added \(totalSteps - oldValue) steps")
}
}
}
}Usage:
let stepCounter = StepCounter()
stepCounter.totalSteps = 200
// About to set totalSteps to 200
// Added 200 steps
stepCounter.totalSteps = 360
// About to set totalSteps to 360
// Added 160 steps
stepCounter.totalSteps = 896
// About to set totalSteps to 896
// Added 536 steps##🐉 State
class Context {
private var state: State = UnauthorizedState()
var isAuthorized: Bool {
get { return state.isAuthorized(self) }
}
var userId: String? {
get { return state.userId(self) }
}
func changeStateToAuthorized(#userId: String) {
state = AuthorizedState(userId: userId)
}
func changeStateToUnauthorized() {
state = UnauthorizedState()
}
}
protocol State {
func isAuthorized(context: Context) -> Bool
func userId(context: Context) -> String?
}
class UnauthorizedState: State {
func isAuthorized(context: Context) -> Bool { return false }
func userId(context: Context) -> String? { return nil }
}
class AuthorizedState: State {
let userId: String
init(userId: String) { self.userId = userId }
func isAuthorized(context: Context) -> Bool { return true }
func userId(context: Context) -> String? { return userId }
}Usage:
let context = Context()
(context.isAuthorized, context.userId)
context.changeStateToAuthorized(userId: "admin")
(context.isAuthorized, context.userId) // now logged in as "admin"
context.changeStateToUnauthorized()
(context.isAuthorized, context.userId)##💡 Strategy
protocol PrintStrategy {
func printString(string: String) -> String
}
class Printer {
let strategy: PrintStrategy
func printString(string: String) -> String {
return self.strategy.printString(string)
}
init(strategy: PrintStrategy) {
self.strategy = strategy
}
}
class UpperCaseStrategy : PrintStrategy {
func printString(string:String) -> String {
return string.uppercaseString
}
}
class LowerCaseStrategy : PrintStrategy {
func printString(string:String) -> String {
return string.lowercaseString
}
}Usage:
var lower = Printer(strategy:LowerCaseStrategy())
lower.printString("O tempora, o mores!")
var upper = Printer(strategy:UpperCaseStrategy())
upper.printString("O tempora, o mores!")##🏃 Visitor
protocol PlanetVisitor {
func visit(planet: PlanetEarth)
func visit(planet: PlanetMars)
func visit(planet: PlanetGliese581C)
}
protocol Planet {
func accept(visitor: PlanetVisitor)
}
class PlanetEarth: Planet {
func accept(visitor: PlanetVisitor) { visitor.visit(self) }
}
class PlanetMars: Planet {
func accept(visitor: PlanetVisitor) { visitor.visit(self) }
}
class PlanetGliese581C: Planet {
func accept(visitor: PlanetVisitor) { visitor.visit(self) }
}
class NameVisitor: PlanetVisitor {
var name = ""
func visit(planet: PlanetEarth) { name = "Earth" }
func visit(planet: PlanetMars) { name = "Mars" }
func visit(planet: PlanetGliese581C) { name = "Gliese 581 C" }
}Usage:
let planets: [Planet] = [PlanetEarth(), PlanetMars(), PlanetGliese581C()]
let names = planets.map { (planet: Planet) -> String in
let visitor = NameVisitor()
planet.accept(visitor)
return visitor.name
}
names🍺 Playground generated with: Swift Playground Builder by @jasonsandmeyer
🚀 How to generate playground (+zip) from this README: GENERATE.markdown