STRATEGY

admin管理员组

文章数量:1794759

STRATEGY

定义

Strategy is a behavioral design pattern that lets you define a family of algorithms, put each of them into a separate class,and make their objects interchangeable.

类图

示例代码 using System; using System.Collections.Generic; namespace RefactoringGuru.DesignPatterns.Strategy.Conceptual { // The Context defines the interface of interest to clients. class Context { // The Context maintains a reference to one of the Strategy objects. The // Context does not know the concrete class of a strategy. It should // work with all strategies via the Strategy interface. private IStrategy _strategy; public Context() { } // Usually, the Context accepts a strategy through the constructor, but // also provides a setter to change it at runtime. public Context(IStrategy strategy) { this._strategy = strategy; } // Usually, the Context allows replacing a Strategy object at runtime. public void SetStrategy(IStrategy strategy) { this._strategy = strategy; } // The Context delegates some work to the Strategy object instead of // implementing multiple versions of the algorithm on its own. public void DoSomeBusinessLogic() { Console.WriteLine("Context: Sorting data using the strategy (not sure how it'll do it)"); var result = this._strategy.DoAlgorithm(new List<string> { "a", "b", "c", "d", "e" }); string resultStr = string.Empty; foreach (var element in result as List<string>) { resultStr += element + ","; } Console.WriteLine(resultStr); } } // The Strategy interface declares operations common to all supported // versions of some algorithm. // // The Context uses this interface to call the algorithm defined by Concrete // Strategies. public interface IStrategy { object DoAlgorithm(object data); } // Concrete Strategies implement the algorithm while following the base // Strategy interface. The interface makes them interchangeable in the // Context. class ConcreteStrategyA : IStrategy { public object DoAlgorithm(object data) { var list = data as List<string>; list.Sort(); return list; } } class ConcreteStrategyB : IStrategy { public object DoAlgorithm(object data) { var list = data as List<string>; list.Sort(); list.Reverse(); return list; } } class Program { static void Main(string[] args) { // The client code picks a concrete strategy and passes it to the // context. The client should be aware of the differences between // strategies in order to make the right choice. var context = new Context(); Console.WriteLine("Client: Strategy is set to normal sorting."); context.SetStrategy(new ConcreteStrategyA()); context.DoSomeBusinessLogic(); Console.WriteLine(); Console.WriteLine("Client: Strategy is set to reverse sorting."); context.SetStrategy(new ConcreteStrategyB()); context.DoSomeBusinessLogic(); } } }

本文标签： strategy