Behavioural Design Pattern: Strategy Design pattern

Level : Advanced
Mentor: Shailendra Chauhan
Duration : 00:01:00

Define Strategy Design pattern

This design defines a set of algorithms, encapsulates each one, and makes them interchangeable. It enables a client to select an algorithm from a family of algorithms at runtime and provides a simple interface to access it.

Examples of Strategy Patterns

Examples of strategy patterns include:

  • Discount Strategy
  • Payment Strategy

Strategy Pattern with UML diagram

The classes, interfaces, & objects in the above UML class diagram are defined as follows:

  • Context: This is a class with a property that stores the reference to a Strategy object. This property will be set at runtime based on the necessary algorithm.
  • Strategy: This interface allows the Context object to call the algorithm provided by a ConcreteStrategy.
  • ConcreteStrategyA/B: These classes implement the Strategy interface.

When Should the Strategy Design Pattern Be Used?

The Strategy design pattern is applicable in the following scenarios:

  • There are several strategies for a given problem, and the selection criteria for each strategy are established at runtime.
  • Many related classes just differ in their behavior.
  • The strategies rely on data to which the client has no access.

Advantages of the Strategy Design Pattern

  • Flexibility: The ability to flexibly change the behavior of an object.
  • Loose Coupling: The strategy classes are independent of one other and the context class, allowing for loose coupling.
  • Reuse: Strategies can be applied in a variety of settings.
  • Isolation: Each approach may be implemented and maintained independently of the others.
  • Open/Closed Principle: New strategies can be implemented without altering the context.
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