The Strategy Design Pattern is a behavioral pattern that enables selecting an algorithm’s behavior at runtime. It defines a family of algorithms, encapsulates each one, and makes them interchangeable. The pattern allows the algorithm to vary independently from the clients that use it, promoting the Open/Closed Principle by enabling easy addition of new strategies without modifying existing code.
- Travel Navigation Methods: When planning a trip, you can choose different travel strategies — by car, bike, or public transport. The route depends on the selected strategy.
- Animal Hunting Techniques: Different animals use various hunting strategies — e.g., lions hunt in groups, owls use stealth, spiders use webs. The hunting goal is the same, but the strategy varies.
- Cooking Techniques: Preparing an egg can involve boiling, frying, or scrambling — each is a strategy to achieve the same goal (cooked egg).
- Payment Methods: At a store, you can pay via cash, credit card, or mobile wallet. Each payment type follows a different internal process (strategy) but serves the same purpose.
- Sorting Algorithms in Libraries: Many libraries use the Strategy pattern to allow users to plug in different sorting strategies (e.g., quicksort, mergesort, bubblesort) depending on the context or data size.
- Game AI Behavior: In games, enemies might switch between different strategies like aggressive, defensive, or evasive based on game state, implemented using interchangeable strategy classes.
- Data Compression or Encryption: Systems often support multiple algorithms for tasks like compression (e.g., ZIP, GZIP) or encryption (e.g., AES, RSA), which can be swapped via a strategy interface.
- Strategy Interface: Define a common interface for all strategies to ensure they are interchangeable and used polymorphically by the client.
- Encapsulation of Behavior: Each algorithm is encapsulated in a separate class, isolating it from other parts of the system and making it easier to test and maintain.
- Runtime Flexibility: The strategy can be selected at runtime, either manually or programmatically, allowing systems to adapt their behavior dynamically.
- Avoid Conditional Logic: Instead of using multiple if-else or switch statements, delegate the behavior to different strategy implementations to clean up the codebase.