I also designed the mode -- 2. Abstract Factory

This mode is a high-level abstraction of a simple factory. The UML diagram is as follows:

Public abstract class abstractfactory
{
Public abstract abstractproducta createproducta ();
Public abstract abstractproductb createproductb ();
}

Public class concretefactory1: abstractfactory
{
Public override abstractproducta createproducta ()
{
Return new producta1 ();
}

Public override abstractproductb createproductb ()
{
Return new productb1 ();
}
}

Public class concretefactory2: abstractfactory
{
Public override abstractproducta createproducta ()
{
Return new producta2 ();
}

Public override abstractproductb createproductb ()
{
Return new productb2 ();
}
}

Public abstract class abstractproducta {}

Public class producta1: abstractproducta {}

Public class producta2: abstractproducta {}


Public abstract class abstractproductb {}

Public class productb1: abstractproductb {}

Public class productb2: abstractproductb {}

Therefore, on the client side, interface-oriented programming can be used as follows:
Abstractfactory AF = new concretefactory1 ();
Abstractproducta APA = AF. createproducta ();
Abstractproductb APB = AF. createproductb ();

Abstract Factory, applicable to a set of product series, that is, it is easy to add a product-as long as three classes of producta3, productb3, and concretefactoryare added at the same time; it is not easy to add a method to operate ACTC-you can use the decorator mode to complete this function.

You can think about it using DB: A simple factory must generate a subclass for each database, and each subclass must implement the same method-there may be code redundancy; abstract Factory abstracts base classes such as abstractconnnection and abstractcommand respectively. Note that it is easy to add a subclass of oledbfactory and oledbconnection and oledbcommand, rather than adding a base class of abstractadapter.