Strategy Pattern: Design pattern in Software design

Understanding the Strategy Pattern in Software Design

You’re about to embark on a wild ride through the world of the Strategy Pattern — expect algorithmic acrobatics, code capers, and a dash of Kotlin comedy. Buckle up, folks, we’re going to make software design patterns fun (or at least try)!

I was rewriting a payment module (taking care of Technical Debt) in a project and reading about a couple of design patters and their usages and recommendations. One of my concern was to write it in a way that addition of a new payment gateway or removal of existing one would be as easy as possible. Although there are a lot of ways to do it, I picked one and we’ll discuss its usages here.

Introduction

In the realm of software design, the Strategy Pattern is a significant design pattern that is used to create an interchangeable family of algorithms from which the required process can be chosen at run time. This blog post seeks to provide an in-depth understanding of the Strategy Pattern with Kotlin code examples, its benefits, usage, and how it influences software architecture.

What is the Strategy Pattern?

The Strategy Pattern, also known as the Policy Pattern, is a behavioral software design pattern that enables selecting an algorithm at runtime. Instead of implementing a single algorithm directly, code receives run-time instructions as to which in a family of algorithms to use. In essence, it defines a family of algorithms, encapsulates each one, and makes them interchangeable, enabling the algorithm to vary independently from clients that use it.

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For example, consider a simple strategy pattern in Kotlin:

interface PaymentGateway {
    fun processPayment(amount: Double): String
}

class Paypal : PaymentGateway {
    override fun processPayment(amount: Double): String {
        // Implementation for processing payment through PayPal
        return "Payment of $amount processed through PayPal"
    }
}

class Stripe : PaymentGateway {
    override fun processPayment(amount: Double): String {
        // Implementation for processing payment through Stripe
        return "Payment of $amount processed through Stripe"
    }
}

class PaymentContext(private val paymentGateway: PaymentGateway) {
    fun executePayment(amount: Double): String {
        return paymentGateway.processPayment(amount)
    }
}

Using the Strategy Pattern in the form of a PaymentGateway interface and concrete strategies like Paypal and Stripe offers several efficiency and robustness benefits.

Firstly, it allows the system to dynamically choose the payment processing method at runtime. This means that the system can easily adapt to different payment scenarios, increasing its flexibility and efficiency.

Secondly, adding or removing payment gateways is straightforward. When a new payment gateway needs to be added, we simply create a new class that implements the PaymentGateway interface. Similarly to remove a payment gateway, we just need to remove the corresponding class. This makes the system highly maintainable and scalable.

Lastly, by separating the payment processing strategies into their own classes, the system becomes more robust. Each strategy can be developed, tested, and debugged independently of the others, reducing the risk of errors and making the system more reliable overall.

Benefits of the Strategy Pattern

Adopting the Strategy Pattern in software design brings numerous benefits. Firstly, it promotes loose coupling by ensuring that the algorithm used is independent of the clients that use it. Secondly, it provides a means to choose from a family of algorithms dynamically, enhancing flexibility. Finally, it improves code maintainability and readability by organising related algorithms, which simplifies modifications and additions of new behaviours.

Use Cases of the Strategy Pattern

The Strategy Pattern is used extensively in various aspects of software design. It is particularly useful when a class has a method that contains multiple conditional statements to choose and execute a behaviour. By encapsulating these behaviours in separate classes, one can eliminate complex conditional statements. This pattern is also useful in situations where different variants of an algorithm exist, and the client application needs to be able to select among these algorithm variants at runtime.

For instance, using the above Kotlin example, we can choose the strategy dynamically:

fun main() {
    var context = PaymentContext(Paypal())
    println(context.executePayment(100.0))

    context = PaymentContext(Stripe())
    println(context.executePayment(100.0))
}

Conclusion

The Strategy Pattern is a powerful tool in software design that reduces complexity by creating a set of interchangeable algorithms that can be selected dynamically at runtime. Its benefits of loose coupling, flexibility, and improved code maintainability make it an appealing choice for many software design scenarios. Understanding and implementing this pattern appropriately can significantly enhance the quality of your software architecture.

❤️ Finally ❤️

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Thanks, Keep coding. Cheers 🍻!