工厂模式

工厂方法模式通过选取相关的实现类来满足调用组件的请求，调用组件无需了解这些实现。

何时使用

调用组件需要根据不同情况调用多个类的时候可以考虑使用工厂

下面是示例代码

///用基类实现更合适。协议感觉有点怪。特别是下面这个全局函数func createRentalCar(by passengers:Int) -> RentalCar? {var car:RentalCar?switch passengers {case 0...1:car = Sports()case 2...3:car = Compact()case 4...8:car = SUV()case 9...14:car = Minivan()default:car = nil}return car
}///RentalCar.swiftprotocol RentalCar {var name:String { get }var passengers:Int { get }var pricePerDay:Float { get }
}class Compact: RentalCar {var name: String = "VM Golf"var passengers: Int = 3var pricePerDay: Float = 20}class Sports: RentalCar {var name: String = "Porsche Boxter"var passengers: Int = 1var pricePerDay: Float = 100
}class SUV: RentalCar {var name: String = "Cadillac Escalade"var passengers: Int = 8var pricePerDay: Float = 75
}//CarSelector.swift
class CarSelector{class func selectCar(by passengers:Int) -> String?{let car = createRentalCar(by: passengers)return car?.name}
}//main.swift
let passengers = [1,3,5]for p in passengers{print("\(p) passegers: \(CarSelector.selectCar(by: p) ?? "")")
}class PriceCalculator {class func calculatePrice(by passengers:Int,and totalDays:Int) -> Float?{if let car = createRentalCar(by: passengers) {return car.pricePerDay * Float(totalDays)}return nil}
}复制代码

输出

Hello, World!
1 passegers: Porsche Boxter
3 passegers: VM Golf
5 passegers: Cadillac Escalade
Program ended with exit code: 0
复制代码

抽象工厂

和简单工厂不一样的是，这个模式可以提供一组对象。

好处:可以在不修改调用组件的情况下，对其使用的类进行修改

什么时候使用:

当调用组件需要一组互相关联的对象，但这些对象又没有共同的父类和协议的时候。

下面是示例代码。创建一个命令行项目AbstractFactory

///FloorPlans.swift
enum EngineOption : String{case front = "Front"case mid = "Mid"
}protocol Floorplan {var seats:Int{ get }var enginePosition:EngineOption { get }}class ShortFloorplan: Floorplan {var seats: Int = 2var enginePosition: EngineOption = .mid
}class StandardFloorplan: Floorplan {var seats: Int = 4var enginePosition: EngineOption = .front
}class LongFloorplan: Floorplan {var seats: Int = 8var enginePosition: EngineOption = .front
}///Suspension.swift
enum SuspensionOption : String{case standard = "Standard"case sports = "Firm"case soft = "Soft"
}protocol Suspension {var suspensionType:SuspensionOption { get }
}class RoadSuspension: Suspension {var suspensionType: SuspensionOption = .standard
}class OffRoadSuspension: Suspension {var suspensionType: SuspensionOption = .soft
}class RaceSuspension: Suspension {var suspensionType: SuspensionOption = .sports
}///Drivetrains.swift
enum DriveOption : String{case front = "Front"case rear = "Rear"case all = "4WD"
}protocol Drivetrain {var driveType:DriveOption { get }
}class FrontWheelDrive: Drivetrain {var driveType: DriveOption = .front
}class RearWheelDrive: Drivetrain {var driveType: DriveOption = .rear}class AllWheelDrive: Drivetrain {var driveType: DriveOption = .all
}///CarParts.swift
enum Cars : String {case compact = "VM Golf"case sports = "Porsche Boxter"case suv = "Cadillac Escalade"
}struct Car {var carType:Carsvar floor:Floorplanvar suspension:Suspensionvar drive:Drivetrainfunc printDetail() {print("Car type: \(carType.rawValue)")print("Seats : \(floor.seats)")print("Engine : \(floor.enginePosition.rawValue)")print("Suspension : \(suspension.suspensionType.rawValue)")print("Drive : \(drive.driveType.rawValue)")}
}///Abstract.swift
class CarFactory {final class func getFactory(car:Cars) -> CarFactory {var factory:CarFactoryswitch car {case .compact:factory = CompactCarFactory()case .sports:factory = SportsCarFactory()case .suv:factory = SUVCarFactory()}return factory}func createFloorplan() -> Floorplan {fatalError("no implemention")}func createSuspension() -> Suspension {fatalError("no implemention")}func createDrivetrain() -> Drivetrain {fatalError("no implemention")}
}///Concrete.swift
class CompactCarFactory : CarFactory {override func createFloorplan() -> Floorplan {return StandardFloorplan()}override func createSuspension() -> Suspension {return RoadSuspension()}override func createDrivetrain() -> Drivetrain {return FrontWheelDrive()}
}class SportsCarFactory: CarFactory {override func createFloorplan() -> Floorplan {return ShortFloorplan()}override func createSuspension() -> Suspension {return RaceSuspension()}override func createDrivetrain() -> Drivetrain {return RearWheelDrive()}
}class SUVCarFactory: CarFactory {override func createFloorplan() -> Floorplan {return LongFloorplan()}override func createSuspension() -> Suspension {return OffRoadSuspension()}override func createDrivetrain() -> Drivetrain {return AllWheelDrive()}
}复制代码

工程代码下载地址github.com/RockyAo/Des…