Strategy Pattern

The Strategy pattern is categorized under behavioral design patterns because it deals with how objects interact and communicate with each other. It's particularly useful when you have a set of related algorithms or behaviors that can be chosen dynamically at runtime.

This pattern is especially useful in situations where you want to support multiple ways of doing something dynamically or where algorithms need to be selected at runtime based on varying conditions.

Usage Scenarios

1. Sorting Algorithms: Implementing different sorting algorithms (e.g., quicksort, mergesort) that can be dynamically chosen based on the size or characteristics of the data set.
2. File Compression: Implementing different compression algorithms (e.g., ZIP, RAR) that can be selected based on factors like file type or desired compression ratio.
3. Payment Processing: Implementing different payment methods (e.g., credit card, PayPal) that can be selected based on user preferences or availability.
4. Image Processing: Implementing different image filtering or processing algorithms (e.g., grayscale, sepia) that can be chosen based on user input or image characteristics.
5. Authentication Strategies: Implementing different authentication methods (e.g., username/password, OAuth) that can be selected based on security requirements or user preferences.
6. Travel Booking Systems: Implementing different pricing strategies (e.g., peak season, off-peak season) that can be selected based on travel dates or customer segments.
7. Game AI: Implementing different strategies for game AI (e.g., aggressive, defensive) that can be selected based on game state or player actions.

Key Concepts

• Encapsulation: Strategies encapsulate algorithms or behaviors into separate classes, keeping related code together and isolated from the client.
• Interface or Abstract Class: Defines a common interface that all concrete strategies must implement. This allows the context to work with any strategy without knowing its specific details.
• Composition over Inheritance: Uses composition to select algorithms at runtime rather than relying on inheritance, promoting flexibility and avoiding a rigid class hierarchy.
• Flexibility: Allows for dynamic selection and switching of strategies at runtime, based on varying conditions or requirements.
• Promotes Code Reuse: Encourages the reuse of algorithmic implementations across different contexts without duplicating code.
• Context: Contains a reference to the strategy interface and delegates tasks to the current concrete strategy. It remains independent of how each strategy performs its task.
• Clear Separation of Concerns: Separates the responsibility of defining an algorithm from the responsibility of using the algorithm, promoting cleaner and more maintainable code.