The Factory Method Design Pattern: A Modular Approach to Object Creation

Design Patterns

Apr 15th - 2024

By

Belatrix

Exploring the Factory Method in Object-Oriented Programming

In object-oriented programming, the Factory Method is a Creational Design Pattern that provides a way to instantiate objects without specifying the precise class of object that will be created. This pattern involves using a factory method to create and return object instances, rather than instantiating objects directly.

This design pattern enhances code modularity and reduces tight coupling between classes, making the codebase more maintainable. It allows for the creation of objects without exposing the instantiation logic to the client and without the client knowing about which class will be instantiated.

How the Factory Method Pattern Operates

The Factory Method pattern is structured around four key components:

  • Product: This is an interface or abstract class that outlines the methods to be implemented by the ConcreteProduct.
  • Concrete Product(s): These are the classes that implement the Product interface.
  • Creator: An abstract class that declares the factory method.
  • Concrete Creator(s): Classes that implement the factory method and return an instance of the ConcreteProduct.

Implementing the Factory Method in a Project

To illustrate the Factory Method pattern in action, consider a furniture shop application that produces furniture sets in various styles, such as Modern, Classic, and Retro. Each style has different products like armchairs, sofas, and coffee tables. For each style, there is a concrete factory class, such as RetroFurnitureFactory, responsible for creating RetroArmchair, RetroCoffeeTable, and RetroSofa products using specific factory methods like MakeArmchair(), MakeCoffeeTable(), and MakeSofa(). In this scenario, RetroFurnitureFactory acts as a Concrete Creator, while the abstract Creator is represented by the FurnitureFactory class, and the Product is represented by an abstract class at the base of the inheritance hierarchy.

The Factory Method UML Diagram

The UML diagram for the Factory Method pattern in a C# code sample would illustrate the relationships between the Product, Concrete Product(s), Creator, and Concrete Creator(s).

Pros and Cons of the Factory Method Design Pattern

Advantages:

  • Loose Coupling: The pattern encourages loose coupling by not requiring the Creator class to know the exact class of the object that will be instantiated.
  • Encapsulation: It encapsulates the object creation process, allowing changes to be made to the creation process without impacting the rest of the code.
  • Code Reuse: By allowing multiple classes to share a common interface, the pattern promotes code reuse.
  • Extensibility: New ConcreteProduct classes can be added without altering existing code, making the pattern extensible.

Disadvantages:

  • Complexity: The pattern can introduce complexity by necessitating additional classes and interfaces.
  • Overhead: It may add overhead to the application, potentially affecting performance if object creation is a bottleneck.

Factory Method vs. Abstract Factory

While both the Factory Method and Abstract Factory are creational design patterns, they differ in their abstraction level and object creation methods. The Factory Method pattern allows subclasses to determine which class to instantiate and is ideal for creating a single family of classes. The Abstract Factory pattern, however, is used to create families of related or dependent objects without specifying their concrete classes.

When to Use the Factory Method Pattern

The Factory Method pattern is beneficial when:

  • The exact class of the object to be created is not known at runtime.
  • The object creation process needs to be encapsulated.
  • Loose coupling between classes is desired.
  • Code reuse is a priority.

Conclusion

The Factory Method Design Pattern is a valuable tool for creating objects in a way that promotes loose coupling and code reuse. It is especially useful when the class of the object to be created is not known until runtime. This article has explored a C# example of the Factory Method pattern and discussed its benefits and potential drawbacks, as well as appropriate use cases.

The C# 11 source code for this pattern is available on GitHub for further exploration.

Design Patterns

Apr 15th - 2024