我知道有很多关于这两种模式之间差异的帖子，但有一些东西我找不到。
From what I have been reading, I see that the factory method pattern allows you to define how to create a single concrete product but hiding the implementation from the client as they will see a generic product. My first question is about the abstract factory. Is its role to allow you to create families of concrete objects in (that can depend on what specific factory you use) rather than just a single concrete object? Does the abstract factory only return one very large object or many objects depending on what methods you call?
我最后两个问题是关于一句我在很多地方都见过的引语，我不能完全理解:
两者之间的一个区别是
使用抽象工厂模式，a
类委托的责任
对象实例化到另一个对象
通过合成，而工厂
方法模式使用继承和
类依赖于子类来处理
所需的对象实例化。
我的理解是，工厂方法模式有一个Creator接口，它将使ConcreteCreator负责知道要实例化哪个ConcreteProduct。这就是使用继承来处理对象实例化的意思吗?
现在，关于引用，抽象工厂模式是如何通过组合将对象实例化的责任委托给另一个对象的?这是什么意思?在我看来，抽象工厂模式似乎也使用继承来完成构造过程，但我仍然在学习这些模式。
任何帮助，特别是最后一个问题，将非常感激。
为了使它非常简单，界面最小，请关注“//1”:
class FactoryProgram
{
static void Main()
{
object myType = Program.MyFactory("byte");
Console.WriteLine(myType.GetType().Name);
myType = Program.MyFactory("float"); //3
Console.WriteLine(myType.GetType().Name);
Console.ReadKey();
}
static object MyFactory(string typeName)
{
object desiredType = null; //1
switch (typeName)
{
case "byte": desiredType = new System.Byte(); break; //2
case "long": desiredType = new System.Int64(); break;
case "float": desiredType = new System.Single(); break;
default: throw new System.NotImplementedException();
}
return desiredType;
}
}
这里的要点:1。Factory和AbstractFactory机制必须使用继承(System。对象->字节，浮点…所以如果你在程序中有继承，那么根据设计2，工厂(抽象工厂很可能不在那里)已经在那里了。Creator (MyFactory)知道具体类型，因此返回具体类型对象给调用者(Main);在抽象工厂中，返回类型是一个接口。
interface IVehicle { string VehicleName { get; set; } }
interface IVehicleFactory
{
IVehicle CreateSingleVehicle(string vehicleType);
}
class HondaFactory : IVehicleFactory
{
public IVehicle CreateSingleVehicle(string vehicleType)
{
switch (vehicleType)
{
case "Sports": return new SportsBike();
case "Regular":return new RegularBike();
default: throw new ApplicationException(string.Format("Vehicle '{0}' cannot be created", vehicleType));
}
}
}
class HeroFactory : IVehicleFactory
{
public IVehicle CreateSingleVehicle(string vehicleType)
{
switch (vehicleType)
{
case "Sports": return new SportsBike();
case "Scooty": return new Scooty();
case "DarkHorse":return new DarkHorseBike();
default: throw new ApplicationException(string.Format("Vehicle '{0}' cannot be created", vehicleType));
}
}
}
class RegularBike : IVehicle { public string VehicleName { get { return "Regular Bike- Name"; } set { VehicleName = value; } } }
class SportsBike : IVehicle { public string VehicleName { get { return "Sports Bike- Name"; } set { VehicleName = value; } } }
class RegularScooter : IVehicle { public string VehicleName { get { return "Regular Scooter- Name"; } set { VehicleName = value; } } }
class Scooty : IVehicle { public string VehicleName { get { return "Scooty- Name"; } set { VehicleName = value; } } }
class DarkHorseBike : IVehicle { public string VehicleName { get { return "DarkHorse Bike- Name"; } set { VehicleName = value; } } }
class Program
{
static void Main(string[] args)
{
IVehicleFactory honda = new HondaFactory(); //1
RegularBike hondaRegularBike = (RegularBike)honda.CreateSingleVehicle("Regular"); //2
SportsBike hondaSportsBike = (SportsBike)honda.CreateSingleVehicle("Sports");
Console.WriteLine("******* Honda **********"+hondaRegularBike.VehicleName+ hondaSportsBike.VehicleName);
IVehicleFactory hero = new HeroFactory();
DarkHorseBike heroDarkHorseBike = (DarkHorseBike)hero.CreateSingleVehicle("DarkHorse");
SportsBike heroSportsBike = (SportsBike)hero.CreateSingleVehicle("Sports");
Scooty heroScooty = (Scooty)hero.CreateSingleVehicle("Scooty");
Console.WriteLine("******* Hero **********"+heroDarkHorseBike.VehicleName + heroScooty.VehicleName+ heroSportsBike.VehicleName);
Console.ReadKey();
}
}
Important points: 1. Requirement: Honda would create "Regular", "Sports" but Hero would create "DarkHorse", "Sports" and "Scooty". 2. why two interfaces? One for manufacturer type(IVehicleFactory) and another for product factory(IVehicle); other way to understand 2 interfaces is abstract factory is all about creating related objects 2. The catch is the IVehicleFactory's children returning and IVehicle(instead of concrete in factory); so I get parent variable(IVehicle); then I create actual concrete type by calling CreateSingleVehicle and then casting parent object to actual child object. What would happen if I do RegularBike heroRegularBike = (RegularBike)hero.CreateSingleVehicle("Regular");; you will get ApplicationException and that's why we need generic abstract factory which I would explain if required. Hope it helps from beginner to intermediate audience.
为了便于理解，考虑这个例子。
电信公司提供什么?例如宽带，电话线和移动电话，你被要求创建一个应用程序，向他们的客户提供他们的产品。
一般来说，你在这里要做的是，通过你的工厂方法创建产品，即宽带，电话线和手机，在那里你知道你为这些产品拥有什么属性，这是非常简单的。
现在，该公司想要为他们的客户提供他们的产品捆绑，即宽带、电话线和移动设备，而抽象工厂就来了。
换句话说，抽象工厂是由其他工厂组成的，他们负责创造自己的产品，抽象工厂知道如何在自己的责任方面把这些产品放在更有意义的地方。
在这种情况下，BundleFactory是抽象工厂，BroadbandFactory, PhonelineFactory和MobileFactory是工厂。为了进一步简化，这些工厂将使用工厂方法初始化各个产品。
运行下面的代码示例:
public class BroadbandFactory : IFactory {
public static Broadband CreateStandardInstance() {
// broadband product creation logic goes here
}
}
public class PhonelineFactory : IFactory {
public static Phoneline CreateStandardInstance() {
// phoneline product creation logic goes here
}
}
public class MobileFactory : IFactory {
public static Mobile CreateStandardInstance() {
// mobile product creation logic goes here
}
}
public class BundleFactory : IAbstractFactory {
public static Bundle CreateBundle() {
broadband = BroadbandFactory.CreateStandardInstance();
phoneline = PhonelineFactory.CreateStandardInstance();
mobile = MobileFactory.CreateStandardInstance();
applySomeDiscountOrWhatever(broadband, phoneline, mobile);
}
private static void applySomeDiscountOrWhatever(Broadband bb, Phoneline pl, Mobile m) {
// some logic here
// maybe manange some variables and invoke some other methods/services/etc.
}
}
希望这能有所帮助。
