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This article mainly introduces the relevant knowledge of "how to achieve abstract factory pattern in Python". The editor shows you the operation process through an actual case. The operation method is simple, fast and practical. I hope this article "how to realize abstract factory pattern in Python" can help you solve the problem.

Reality

Here are some useful techniques for implementing the Abstract Factor pattern:

1) treat the factory as a single piece in an application that generally requires only one ConcreteFactory for each product line. So the factory is usually best implemented as a Singleton (3. 5).

There is only one sentence, but no implementation is given. In order to illustrate this problem, according to his own understanding, the author provides an implementation with the example of the operating system topic mentioned above as the background.

Class diagram:

The Singleton design pattern will be covered in more detail in subsequent articles, which will be briefly mentioned here.

Constructors and destructors are first made protected in ThemeFactory, so that there is no way for users to build and destroy factory objects directly. Users can build and destroy objects using two additional exposed static methods: getInstance and deleteInstance. This is how the Sington pattern ensures that only one object exists at a time.

You should already be familiar with the createWindow and createScrobar interfaces of the generated product.

Header file

First of all, look at the include statement part. In order to control the creation and destruction of the concrete class, the implementation of the abstract class contains three header files of the concrete class. Generally speaking, it doesn't feel good. This problem can be solved, but it will be cumbersome. There will be no further discussion here.

Next, there are two static variables: instance to hold the unique instance of the representational class of ThemeFactory, and system_theme to hold the settings for the system. Since this is a demo program, such a variable is used to control the operation of the program.

The rest of the code is simpler, which is not explained here.

User code

First of all, notice that only the header file of the abstract class is included here. And because the header file of the abstract class does not contain the header file of the elephant class, the concrete class is completely invisible to the user. When the theme of the system changes, the switch of the concrete factory class is realized automatically.

Execution result

Pay attention to the switching action of the factory.

That's all for "how Python implements Abstract Factory patterns". Thank you for reading. If you want to know more about the industry, you can follow the industry information channel. The editor will update different knowledge points for you every day.

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