开关语句是否适用于工厂方法？ C＃ [英] Is a switch statement applicable in a factory method? c#

问题描述

我想返回一个接口，并在我要设置的switch语句里面。这是一个糟糕的设计吗？

  private IResultEntity GetEntity（char？someType）
 {
 IResultEntity entity =空值; 
 
 switch（someType）
 {
 case'L'：// life 
 entity = new LifeEntity（）; 
 break; 
 case'P'：// property 
 entity = new PropertyEntity（）; 
 break; 
 case'D'：// disability 
 entity = new DisabilityEntity（）; 
 break; 
 case'C'：//信用卡
 entity = new CreditCardEntity（）; 
 break; 
} 
 
返回实体; 
} 
  

解决方案

我通常不介意在工厂中切换语句，前提是我可以组合和控制我希望我的工厂提前创建的所有派生类。

有时，也许用户创建的插件可能希望将自己的类添加到该开关列表，然后是一个swich语句是不够的。

我发现这个很好来源的更多信息创建一些更强大/多才多艺的工厂课程

一个好的我通常采取的中间方法是保持静态字典<字符串，类型>为每个工厂类。

人们可以使用某种

pre> Factories.TypeRegistration.StaticDictionary.Add（somekey，typeof（MyDerivedClass））


（或更好的是使用注册方法并隐藏StaticDictionary）

然后，Factory通过执行一个简单的任务来创建一个实例在表中查找：

  Activator.CreateInstance（Factories.TypeRegistration.StaticDictionary [somekey]）; 
  

I want to return an Interface and inside a switch statement I would like to set it. Is this a bad design?

private IResultEntity GetEntity(char? someType)
    {
        IResultEntity entity = null;

        switch (someType)
        {
            case 'L': //life
                entity = new LifeEntity();
                break;
            case 'P': //property
                entity = new PropertyEntity();
                break;
            case 'D': //disability
                entity = new DisabilityEntity();
                break;
            case 'C': //credit card
                entity = new CreditCardEntity();
                break;
        }

        return entity;
    }

解决方案

I don't usually mind switch statements in a factory, provided I can group and control all of the derived classes that I want my factory to create in advance.

Sometimes,maybe a user-created plugin might want to add it's own classes to that switch list, and then a swich statement is not enough.

I found this good source for some more info on creating some more powerfull/versatile factory classes

A good middle-ground approach I usually take is to keep a static Dictionary< string,Type > for each factory class.

People can just "register" their own implementations using some sort of

Factories.TypeRegistration.StaticDictionary.Add("somekey",typeof(MyDerivedClass))

(or better yet, use a Registration method and hide the StaticDictionary)

then the Factory has an easy task of creating an instance by performing a lookup in the table:

Activator.CreateInstance(Factories.TypeRegistration.StaticDictionary["somekey"]);

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