Summary

In this chapter, we have seen how to use the Factory Method and the Abstract Factory design patterns. Both patterns are used when we want to (a) track an object creation, (b) decouple an object creation from an object usage, or even (c) improve the performance and resource usage of an application. Case (c) was not demonstrated in the chapter. You might consider it as a good exercise.

The Factory Method design pattern is implemented as a single function that doesn't belong to any class, and is responsible for the creation of a single kind of object (a shape, a connection point, and so on). We saw how the Factory Method relates to toy construction, mentioned how it is used by Django for creating different form fields, and discussed other possible use cases for it. As an example, we implemented a Factory Method that provides access to the XML and JSON files.

The Abstract Factory design pattern is implemented as a number of Factory Methods that belong to a single class and are used to create a family of related objects (the parts of a car, the environment of a game, and so forth). We mentioned how the Abstract Factory is related with car manufacturing, how the django_factory Django package makes use of it to create clean tests, and covered the use cases of it. The implementation of the Abstract Factory is a mini-game that shows how we can use many related factories in a single class.

In the next chapter, we will talk about the Builder pattern, which is another creational pattern that can be used for fine-controlling the creation of complex objects.