Understanding the Strategy Design Pattern
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Introduction to the Strategy Design Pattern
The Strategy Design Pattern is a behavioral design pattern that enables selecting an algorithm’s behavior at runtime. Instead of implementing a single algorithm directly, the code receives runtime instructions specifying which of a family of methods to use.
Key Concepts
- Strategy Interface: This defines a common interface for all supported algorithms. Any algorithm that implements the interface can be used interchangeably by the client that utilizes the strategies.
- Concrete Strategies: These are classes that implement the Strategy interface, providing specific behaviors.
- Context: A class that contains a reference to a Strategy object. The context delegates the work to the strategy object instead of executing its own algorithm.
Benefits
- Flexibility: Easily switch between different algorithms used by an object at runtime.
- Decoupling: The high level of decoupling between the context and the strategies allows for better manageability and scalability.
- Open/Closed Principle: You can introduce new strategies without changing the context’s code, adhering to this SOLID principle.
Example in Code
Here’s how you might implement the Strategy Pattern in C# for a simple application that can switch its behavior at runtime:
// Strategy interfacepublic interface IStrategy{ void Execute();}
// Concrete strategiespublic class ConcreteStrategyA : IStrategy{ public void Execute() { Console.WriteLine("Executing Strategy A"); }}
public class ConcreteStrategyB : IStrategy{ public void Execute() { Console.WriteLine("Executing Strategy B"); }}
// Context classpublic class Context{ private IStrategy _strategy;
public Context(IStrategy strategy) { this._strategy = strategy; }
public void SetStrategy(IStrategy strategy) { this._strategy = strategy; }
public void ExecuteStrategy() { _strategy.Execute(); }}
// Example usageclass Program{ static void Main(string[] args) { var context = new Context(new ConcreteStrategyA()); context.ExecuteStrategy(); context.SetStrategy(new ConcreteStrategyB()); context.ExecuteStrategy(); }}