Table of Contents

1. Introduction
2. Key Characteristics of the Factory Method
3. Imagine This Scenario
4. How This Relates to the Factory Method
5. Problems Solved by the Factory Method
6. Example in PHP
7. Pros and Cons of the Factory Method
8. Summary
9. Key Takeaways

Introduction :

The Factory Method is a creational design pattern that provides an interface for creating objects in a superclass but allows subclasses to alter the type of created objects. This pattern is particularly useful when the exact type of the object to be created is not known until runtime.

Key Characteristics of the Factory Method

• Decoupling: It removes the instantiation logic from the client code, promoting loose coupling.
• Subclasses: Subclasses can override the factory method to create objects of a specific type.
• Interface: The pattern defines an interface for creating an object, but lets subclasses decide which class to instantiate.

Imagine This Scenario

To grasp the Factory Method better, let’s consider a real-world analogy, like ordering different types of pizzas:

1. Pizza Shop: Think of a pizza shop where you can order pizzas. The shop has a menu with various types of pizzas, but you don’t need to know how each pizza is made.

2. Order Process: When you place an order, you choose which type of pizza you want. The pizza shop has a method for preparing your chosen pizza, but each type of pizza may require a different recipe or ingredients.

3. Customization: If tomorrow you want a new type of pizza, the shop can simply add a new recipe without changing how customers place their orders.

How This Relates to the Factory Method

• Decoupling Creation: Just like the pizza shop doesn’t require customers to know how each pizza is made, the Factory Method allows clients to create objects without knowing the concrete classes.

• Overriding Creation: If you want to introduce a new type of pizza (e.g., Vegan Pizza), you would create a new subclass that overrides the factory method to handle this specific pizza creation.

Problems Solved by the Factory Method

The Factory Method pattern addresses several common issues in software design:

1. Tight Coupling: It reduces tight coupling between client code and concrete classes, allowing new types to be introduced without altering existing code.

2. Code Scalability: As your application grows, adding new object types becomes easier and cleaner. You can simply create new subclasses without modifying the core functionality.

3. Complex Object Creation: It simplifies complex object creation processes by encapsulating instantiation logic within factory methods, allowing for cleaner and more maintainable code.

4. Testing and Mocking: The pattern facilitates easier testing since you can mock or stub the factory method during unit tests, making it simpler to test components in isolation.

Example in PHP

Here’s a simple implementation of the Factory Method pattern in PHP:

// Product Interface
interface Pizza {
    public function prepare();
}

// Concrete Products
class CheesePizza implements Pizza {
    public function prepare() {
        echo "Preparing Cheese Pizza!";
    }
}

class PepperoniPizza implements Pizza {
    public function prepare() {
        echo "Preparing Pepperoni Pizza!";
    }
}

// Creator Class
abstract class PizzaShop {
    abstract protected function createPizza($type);

    public function orderPizza($type) {
        $pizza = $this->createPizza($type);
        $pizza->prepare();
        return $pizza;
    }
}

// Concrete Creator
class SimplePizzaShop extends PizzaShop {
    protected function createPizza($type) {
        switch ($type) {
            case 'cheese':
                return new CheesePizza();
            case 'pepperoni':
                return new PepperoniPizza();
            default:
                throw new Exception("Unknown pizza type.");
        }
    }
}

// Using the Factory Method
$pizzaShop = new SimplePizzaShop();
$pizzaShop->orderPizza('cheese'); // Preparing Cheese Pizza!
$pizzaShop->orderPizza('pepperoni'); // Preparing Pepperoni Pizza!

Pros and Cons of the Factory Method

Pros

• Flexibility: New types can be added with minimal changes to existing code.
• Encapsulation: Object creation logic is encapsulated in the factory method, promoting cleaner code.
• Improved Maintainability: Reduces the risk of breaking existing functionality when introducing new classes.
• Supports Open/Closed Principle: The pattern adheres to this principle by allowing the system to be open for extension but closed for modification.

Cons

• Increased Complexity: Introduces additional classes and interfaces, which may complicate the design.
• Potential Overhead: If not used judiciously, it may lead to unnecessary complexity when simple object creation suffices.
• Learning Curve: Beginners may find it challenging to understand when and how to implement this pattern effectively.

Summary

In this analogy:

• The PizzaShop represents our factory class.
• The Concrete Products (CheesePizza, PepperoniPizza) are the different types of objects created.
• The orderPizza() method is the factory method that handles object creation without exposing the instantiation logic to the client.

Just like how a pizza shop can handle various orders without customers needing to know the details of each recipe, the Factory Method pattern simplifies object creation and promotes flexibility in your application design.

This pattern is vital for creating scalable and maintainable code, especially when working with complex systems that require multiple object types.

Key Takeaways

• Problems Solved: It reduces tight coupling, enhances scalability, simplifies complex object creation, and supports easier testing.
• Pros: Offers flexibility, encapsulation, improved maintainability, and supports the Open/Closed Principle.
• Cons: Introduces complexity, potential overhead, and may have a learning curve for beginners.

The Factory Method is a powerful tool in a software developer's toolkit that helps manage object creation efficiently while maintaining a clean and organized codebase.

Refactoring Guru - Factory Method