Factories

The factory method is one of the twenty-three Gang of Four design patterns.

The problem they solve

• How can an object be created so that subclasses can redefine which class to instantiate?

How they achieve this

• Define the factory method, which is a separate operation for creating an object.

• Create an object by calling a factory method.

This enables the writing of subclasses to change the way an object is created.

It helps with the interface segregation principle and dependency inversion principle of the SOLID best practices.

Other benefits include:

• Easier to implement inversion of control.

• More testable as you can mock interfaces.

• A lot easier to change the application after shipping, as you can create new implementations without changing the dependent code.