Strategy Pattern

The Strategy Pattern is a behavioral design pattern that enables the selection of an algorithm at runtime from a family of algorithms. By encapsulating each algorithm and making them interchangeable, the pattern ensures that the client using the algorithm can remain decoupled from the specific implementation. This makes the pattern especially useful for scenarios where behavior may vary dynamically.

Why Use the Strategy Pattern?

When designing software, objects often have states and behaviors, and some of these behaviors may vary depending on the context. The Strategy Pattern focuses on these dynamic behaviors by:

• Defining a family of algorithms.
• Encapsulating each algorithm in its own class.
• Allowing the client to switch between these algorithms at runtime.

Benefits of the Strategy Pattern

• Open/Closed Principle: The system is open to extensions but closed to modifications.
• Improved Maintainability: Changes to algorithms do not affect the client.
• Reusability: Algorithms can be reused across different contexts.

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Example: A Discount System for Customers

Let’s explore the Strategy Pattern with a simple example: implementing a discount system for a retail application. Customers receive discounts based on their total sales amount, and the discount strategies vary depending on predefined thresholds.

Key Components of the Strategy Pattern

1. IDiscountStrategy: An interface defining the method for applying discounts.
2. Concrete Strategies: Classes implementing the discount logic:
   • NoDiscountStrategy
   • LowDiscountStrategy
   • MediumDiscountStrategy
   • HighDiscountStrategy
3. CustomerDiscountContext: A context class that selects and uses the appropriate discount strategy.
4. Program.cs: The main program demonstrating the Strategy Pattern in action.

https://github.com/stevsharp/StrategyPattern

References

• Design Patterns: Elements of Reusable Object-Oriented Software by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides.
• Microsoft Docs: Behavioral Design Patterns
• Refactoring Guru: Strategy Pattern