It allows a calling component to obtain a family or group of related objects without needing to know which classes were used to create them.
每一层的创建都是工厂，并且客户端和中间层是不知道具体零件的类型的。
client:
let car = Car(carType: Cars.SPORTS);
car.printDetails();
design pattern:
enum Cars: String {
case COMPACT = "VW Golf";
case SPORTS = "Porsche Boxter";
case SUV = "Cadillac Escalade";
}
struct Car {
var carType:Cars;
var floor:Floorplan;
var suspension:Suspension;
var drive:Drivetrain;
init(carType:Cars) {
let concreteFactory = CarFactory.getFactory(carType);
self.floor = concreteFactory!.createFloorplan();
self.suspension = concreteFactory!.createSuspension();
self.drive = concreteFactory!.createDrivetrain();
self.carType = carType;
}
func printDetails() {
println("Car type: \(carType.rawValue)");
println("Seats: \(floor.seats)");
println("Engine: \(floor.enginePosition.rawValue)");
println("Suspension: \(suspension.suspensionType.rawValue)");
println("Drive: \(drive.driveType.rawValue)");
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class CarFactory {
required init() {
// do nothing
}
func createFloorplan() -> Floorplan {
fatalError("Not implemented");
}
func createSuspension() -> Suspension {
fatalError("Not implemented");
}
func createDrivetrain() -> Drivetrain {
fatalError("Not implemented");
}
final class func getFactory(car:Cars) -> CarFactory? {
var factoryType:CarFactory.Type;
switch (car) {
case .COMPACT:
factoryType = CompactCarFactory.self;
case .SPORTS:
factoryType = SportsCarFactory.self;
case .SUV:
factoryType = SUVCarFactory.self;
}
var factory = factoryType.sharedInstance;
if (factory == nil) {
factory = factoryType();
}
return factory;
}
class var sharedInstance:CarFactory? {
get {
return nil;
}
}
}
class CompactCarFactory : CarFactory {
override func createFloorplan() -> Floorplan {
return StandardFloorplan();
}
override func createSuspension() -> Suspension {
return RoadSuspension.getInstance();
}
override func createDrivetrain() -> Drivetrain {
return FrontWheelDrive();
}
}
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
protocol Floorplan {
var seats:Int { get }
var enginePosition:EngineOption { get };
}
enum EngineOption : String {
case FRONT = "Front"; case MID = "Mid";
}
class ShortFloorplan: Floorplan {
var seats = 2;
var enginePosition = EngineOption.MID
}
