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)");

}

}