记录一本设计模式的书

常用设计模式有哪些？

策略设计模式

这里有一个 策略模式 C# 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 { \"a\", \"b\", \"c\", \"d\", \"e\" }); string resultStr = string.Empty; foreach (var element in result as List) { 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; list.Sort(); return list; } } class ConcreteStrategyB : IStrategy { public object DoAlgorithm(object data) { var list = data as List; 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(); } }}

 Output.txt: 执行结果

Client: Strategy is set to normal sorting.Context: Sorting data using the strategy (not sure how it\'ll do it)a,b,c,d,eClient: Strategy is set to reverse sorting.Context: Sorting data using the strategy (not sure how it\'ll do it)e,d,c,b,a

原文链接：C# 策略模式讲解和代码示例

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