策略模式

策略模式作爲一種軟件設計模式，指對象有某個行爲，但是在不同的場景中，該行爲有不同的實現算法。比如每個人都要“交個人所得稅”，但是“在美國交個人所得稅”和“在中華民國交個人所得稅”就有不同的算稅方法。 策略模式： 定义了一族算法（业务规则）； 封装了每个算法； 这族的算法可互换代替（interchangeable）。 #include <iostream> using namespace std; class StrategyInterface { public: virtual void execute() = 0; }; class ConcreteStrategyA: public StrategyInterface { public: virtual void execute() { cout << "Called ConcreteStrategyA execute method" << endl; } }; class ConcreteStrategyB: public StrategyInterface { public: virtual void execute() { cout << "Called ConcreteStrategyB execute method" << endl; } }; class ConcreteStrategyC: public StrategyInterface { public: virtual void execute() { cout << "Called ConcreteStrategyC execute method" << endl; } }; class Context { private: StrategyInterface *_strategy; public: Context(StrategyInterface *strategy):_strategy(strategy) { } void set_strategy(StrategyInterface *strategy) { _strategy = strategy; } void execute() { _strategy->execute(); } }; int main(int argc, char *argv[]) { ConcreteStrategyA concreteStrategyA; ConcreteStrategyB concreteStrategyB; ConcreteStrategyC concreteStrategyC; Context contextA(&concreteStrategyA); Context contextB(&concreteStrategyB); Context contextC(&concreteStrategyC); contextA.execute(); contextB.execute(); contextC.execute(); contextA.set_strategy(&concreteStrategyB); contextA.execute(); contextA.set_strategy(&concreteStrategyC); contextA.execute(); return 0; } //StrategyExample test application class StrategyExample { public static void main(String[] args) { Context context; // Three contexts following different strategies context = new Context(new FirstStrategy()); context.execute(); context = new Context(new SecondStrategy()); context.execute(); context = new Context(new ThirdStrategy()); context.execute(); } } // The classes that implement a concrete strategy should implement this // The context class uses this to call the concrete strategy interface Strategy { void execute(); } // Implements the algorithm using the strategy interface class FirstStrategy implements Strategy { public void execute() { System.out.println("Called FirstStrategy.execute()"); } } class SecondStrategy implements Strategy { public void execute() { System.out.println("Called SecondStrategy.execute()"); } } class ThirdStrategy implements Strategy { public void execute() { System.out.println("Called ThirdStrategy.execute()"); } } // Configured with a ConcreteStrategy object and maintains a reference to a Strategy object class Context { Strategy strategy; // Constructor public Context(Strategy strategy) { this.strategy = strategy; } public void execute() { this.strategy.execute(); } } using System; namespace Wikipedia.Patterns.Strategy { // MainApp test application class MainApp { static void Main() { Context context; // Three contexts following different strategies context = new Context(new ConcreteStrategyA()); context.Execute(); context = new Context(new ConcreteStrategyB()); context.Execute(); context = new Context(new ConcreteStrategyC()); context.Execute(); } } // The classes that implement a concrete strategy should implement this // The context class uses this to call the concrete strategy interface IStrategy { void Execute(); } // Implements the algorithm using the strategy interface class ConcreteStrategyA : IStrategy { public void Execute() { Console.WriteLine( "Called ConcreteStrategyA.Execute()" ); } } class ConcreteStrategyB : IStrategy { public void Execute() { Console.WriteLine( "Called ConcreteStrategyB.Execute()" ); } } class ConcreteStrategyC : IStrategy { public void Execute() { Console.WriteLine( "Called ConcreteStrategyC.Execute()" ); } } // Configured with a ConcreteStrategy object and maintains a reference to a Strategy object class Context { IStrategy strategy; // Constructor public Context(IStrategy strategy) { this.strategy = strategy; } public void Execute() { strategy.Execute(); } } } //invoked from application.initialize private function init() : void { var context:Context; context = new Context( new ConcreteStrategyA() ); context.execute(); context = new Context( new ConcreteStrategyB() ); context.execute(); context = new Context( new ConcreteStrategyC() ); context.execute(); } package org.wikipedia.patterns.strategy { public interface IStrategy { function execute() : void ; } } package org.wikipedia.patterns.strategy { public final class ConcreteStrategyA implements IStrategy { public function execute():void { trace( "ConcreteStrategyA.execute(); invoked" ); } } } package org.wikipedia.patterns.strategy { public final class ConcreteStrategyB implements IStrategy { public function execute():void { trace( "ConcreteStrategyB.execute(); invoked" ); } } } package org.wikipedia.patterns.strategy { public final class ConcreteStrategyC implements IStrategy { public function execute():void { trace( "ConcreteStrategyC.execute(); invoked" ); } } } package org.wikipedia.patterns.strategy { public class Context { private var strategy:IStrategy; public function Context(strategy:IStrategy) { this.strategy = strategy; } public function execute() : void { strategy.execute(); } } } <?php class StrategyExample { public function __construct() { $context = new Context(new ConcreteStrategyA()); $context->execute(); $context = new Context(new ConcreteStrategyB()); $context->execute(); $context = new Context(new ConcreteStrategyC()); $context->execute(); } } interface IStrategy { public function execute(); } class ConcreteStrategyA implements IStrategy { public function execute() { echo "Called ConcreteStrategyA execute method\n"; } } class ConcreteStrategyB implements IStrategy { public function execute() { echo "Called ConcreteStrategyB execute method\n"; } } class ConcreteStrategyC implements IStrategy { public function execute() { echo "Called ConcreteStrategyC execute method\n"; } } class Context { var $strategy; public function __construct(IStrategy $strategy) { $this->strategy = $strategy; } public function execute() { $this->strategy->execute(); } } new StrategyExample; ?> @protocol Strategy <NSObject> @required - (void)print; @end @interface ConcreteStrategyA : NSObject<Strategy> { } @end @interface ConcreteStrategyB : NSObject<Strategy> { } @end @interface Context : NSObject { id<Strategy> _strategy; } @property (nonatomic, assign) id<Strategy> strategy; -(void)doIt; @end @implementation ConcreteStrategyA - (void)print { NSLog(@"Test01"); } @end @implementation ConcreteStrategyB - (void)print { NSLog(@"Test02"); } @end @implementation Context @synthesize strategy = _strategy; -(void)doIt { [self.strategy print]; } @end