Transforming a Switch Statement into Polymorphic Deployment in PHP

It this blog post we are going to learn how we can use Polymorphism instead of Switch statement.

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A switch statement is often used when you have multiple cases that depend on a value. Polymorphism can eliminate the need for such conditionals by leveraging object-oriented programming principles, where each class handles its behavior.

Here’s an example:

Before (Using a switch statement):

class PaymentProcessor {
    public function process($paymentType) {
        switch ($paymentType) {
            case 'credit':
                $this->processCredit();
                break;
            case 'paypal':
                $this->processPayPal();
                break;
            case 'bitcoin':
                $this->processBitcoin();
                break;
            default:
                throw new Exception("Unknown payment type");
        }
    }

    private function processCredit() {
        echo "Processing credit payment";
    }

    private function processPayPal() {
        echo "Processing PayPal payment";
    }

    private function processBitcoin() {
        echo "Processing Bitcoin payment";
    }
}

After (Using Polymorphism):

abstract class PaymentMethod {
    abstract public function process();
}

class CreditPayment extends PaymentMethod {
    public function process() {
        echo "Processing credit payment";
    }
}

class PayPalPayment extends PaymentMethod {
    public function process() {
        echo "Processing PayPal payment";
    }
}

class BitcoinPayment extends PaymentMethod {
    public function process() {
        echo "Processing Bitcoin payment";
    }
}

class PaymentProcessor {
    public function process(PaymentMethod $paymentMethod) {
        $paymentMethod->process();
    }
}

// Usage
$paymentProcessor = new PaymentProcessor();
$paymentProcessor->process(new CreditPayment()); // Processing credit payment
$paymentProcessor->process(new PayPalPayment()); // Processing PayPal payment

In the polymorphic version, each payment method has its own class, and the PaymentProcessor delegates the processing to the specific class without needing a switch statement.

Benefits of using Polymorphism:

Using polymorphism instead of a switch statement provides several benefits in terms of code design, maintainability, and scalability:

1. Improved Code Readability and Organization

• Polymorphism: When you use polymorphism, you organize code into separate classes, each handling its own behavior. This makes the code more modular and easier to follow.
• Switch Statement: A switch statement can grow very large and become hard to maintain, especially when handling many cases. The logic for all cases is tightly packed in a single block, making it more difficult to navigate.

2. Scalability and Maintainability

• Polymorphism: Adding new behavior is as simple as adding a new class that implements or extends the base class. You don’t need to modify the existing code, adhering to the Open/Closed Principle of SOLID, where code is open for extension but closed for modification.
• Switch Statement: Every time you add a new case, you have to modify the switch statement, increasing the risk of introducing errors and making it harder to maintain.

3. Separation of Concerns

• Polymorphism: Each class is responsible for its own behavior, keeping logic encapsulated and promoting cleaner, more maintainable code.
• Switch Statement: The logic is centralized, which means as the complexity grows, the single function handling all cases might become bloated.

4. Testability

• Polymorphism: Each class can be individually tested, leading to easier unit testing. It’s easier to mock, stub, or isolate each behavior when testing.
• Switch Statement: Testing each case in a switch statement may require more complex setup, since all the logic is lumped together in a single function.

5. Reduction of Conditional Logic

• Polymorphism: Polymorphism inherently avoids the need for conditionals, since each object or class “knows” what it should do based on the context.
• Switch Statement: Switch statements rely heavily on conditional logic, which can lead to more bugs and harder-to-understand code as complexity increases.

6. Easier to Extend

• Polymorphism: If you need to extend the system, for instance by adding a new behavior, you can simply add a new class or subclass.
• Switch Statement: Extending a switch statement often means directly modifying the existing structure, which can lead to tightly coupled code and potential regressions.

7. Encapsulation

• Polymorphism: Polymorphism enables encapsulation by bundling data with the methods that operate on it, ensuring that only relevant parts of the system are affected when changes occur.
• Switch Statement: A switch statement doesn’t offer encapsulation. It typically manipulates external data, which can lead to unintended side effects if not carefully managed.

Hope you found this helpful!