为什么抽象工厂处理家族和工厂方法生成单个对象？

问题描述

从我所看到的，抽象工厂模式通常关注自己创建几个与同一个系列相关联的对象，而工厂方法模式也涉及生成单个对象。

考虑以下示例，它会翻转这些问题：

  //工厂方法（基类）允许用于创建对象的家族
 public class BasePizzaCreator {
 abstract ISauce CreateSauce（）; 
 abstract IToppings CreateToppings（）; 
抽象ICrust CreateCrust（）; 
} 
 
 //抽象工厂（界面）定义合同创建一个对象
 public interface IPizzaFactory {
 abstract IPizza CreatePizza（）; 
} 
  

很明显，您可以使用它们方式 - 但它是否违反了模式的精神？如果是这样，为什么？

我真正想要了解的是：为什么抽象工厂是创建相关对象系列的更好方法，而Factory方法更好的方法创建单个对象？

解决方案

在给定的示例中， BasePizzaCreator 是一个抽象工厂，但 IPizzaFactory 不是任何GoF设计模式（尽管它有时被称为简单工厂）。

$ b $关于为什么Abstract Factory处理产品系列的原因，而Factory Method处理单个产品：这仅仅是GoF定义的产品。随着GoF书的提及，实现抽象工厂的最常用方法是使用多种工厂方法。从客户的角度来看，抽象工厂可能是优选的，因为客户端通过组合/委托来调用它，而不是Factory Method，需要客户端继承该方法。

最后，注意抽象工厂与工厂方法是Stack Overflow中第二大流行的设计模式主题。不幸的是，有很多（高度高调的）错误信息也被发布，所以当有疑问时，总是回到这本书。

From what I have read, the abstract factory pattern typically concerns itself with creating several objects which are all associated with the same family, and the factory method pattern concerns itself with generating a single object.

Consider the following example, which flips those concerns:

// Factory Method (base class) allowing for creation of families of objects
public class BasePizzaCreator{
    abstract ISauce CreateSauce();
    abstract IToppings CreateToppings();
    abstract ICrust CreateCrust();
}

// Abstract Factory (interface) defining contract to create a single object
public interface IPizzaFactory{
    abstract IPizza CreatePizza();
}

It is obvious that you can use them this way - but is it a violation of the spirit of the patterns? If so, why?

What I really want to understand here is this: Why is Abstract Factory the better approach for creating families of related objects, and Factory method the better approach to creating a single object?

解决方案

In the given examples, BasePizzaCreator is an Abstract Factory, but IPizzaFactory is not any GoF design pattern (though it is sometimes referred to as a Simple Factory).

As to why Abstract Factory deals with product families while Factory Method deals with a single product: that's simply how the GoF defined them. As the GoF book mentions, the most common way to implement an Abstract Factory is with multiple Factory Methods. From a client's perspective, Abstract Factory may be preferable because clients invoke it through composition/delegation, as opposed to Factory Method which requires clients to inherit that method.

Finally, note that "Abstract Factory vs. Factory Method" is the second-most popular design patterns topic on Stack Overflow. Unfortunately, there is a lot of (highly-upvoted) misinformation posted as well, so when in doubt, always refer back to the book.

• Differences between Abstract Factory Pattern and Factory Method
• Design Patterns: Abstract Factory vs Factory Method
• Design Patterns: Factory vs Factory method vs Abstract Factory
• Factory, Abstract Factory and Factory Method

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