Head First设计模式C++实现-Strategy模式

 定义：

  定义了算法族，分别封装起来，让它们之间可以互相替换，以此模式让算法的变化独立于使用算法的客户。

UML图：

代码实现：

/************************************************************************//* Strategy.h *//************************************************************************//** * @file Strategy.h * @brief Strategy模式的实现代码 * @author [e-mail] * http://blog.csdn.net/rabbit729* @version 1.0 * @date 2009-02-23 */ #ifndef STRATEGY_H_#define STRATEGY_H_#include <string>using std::string;class IQuackBehavior{public: virtual string Quacking() = 0; };class IFlyBehavior{public: virtual string Fly() = 0;};class MuteQuack : public IQuackBehavior{public: string Quacking();};class Quack : public IQuackBehavior{public: string Quacking();};class Squeak : public IQuackBehavior{public: string Quacking();};class FlyNoWay : public IFlyBehavior{public: string Fly();};class FlyRocketPowered : public IFlyBehavior{public: string Fly();};class FlyWithWings : public IFlyBehavior{public: string Fly();};class Duck{protected: IFlyBehavior* flyBehavior; IQuackBehavior* quackBehavior;public: void SetFly(IFlyBehavior* flyBehavior); void SetQuack(IQuackBehavior* quackBehavior); virtual string Display() = 0; string PerformFly(); string PerformQuack(); string Swim();};class MallardDuck : public Duck{public: MallardDuck(); string Display();};class ModelDuck : public Duck{public: ModelDuck(); string Display();};class RubberDuck : public Duck{public: RubberDuck(); string Display();};#endif/************************************************************************//* Strategy.cpp *//************************************************************************//** * @file Strategy.cpp * @brief Strategy模式的实现代码 * @author [e-mail] * http://blog.csdn.net/rabbit729* @version 1.0 * @date 2009-02-23 */ #include "Strategy.h"string MuteQuack::Quacking(){ return "silence";}string Quack::Quacking(){ return "Quack";}string Squeak::Quacking(){ return "Squeak";}string FlyNoWay::Fly(){ return "I can't fly.";}string FlyRocketPowered::Fly(){ return "I'm flying with a rocket!";}string FlyWithWings::Fly(){ return "I'm flying!!";}void Duck::SetFly(IFlyBehavior *flyBehavior){ this->flyBehavior = flyBehavior;}void Duck::SetQuack(IQuackBehavior* quackBehavior){ this->quackBehavior = quackBehavior;}string Duck::PerformFly(){ return flyBehavior->Fly();}string Duck::PerformQuack(){ return quackBehavior->Quacking();}string Duck::Swim(){ return "All ducks float, even decoys!";}MallardDuck::MallardDuck(){ quackBehavior = new Quack(); flyBehavior = new FlyWithWings();}string MallardDuck::Display(){ return "I'm a real Mallard duck";}ModelDuck::ModelDuck(){ quackBehavior = new Quack(); flyBehavior = new FlyNoWay();}string ModelDuck::Display(){ return "I'm a model duck";}RubberDuck::RubberDuck(){ quackBehavior = new Squeak(); flyBehavior = new FlyNoWay();}string RubberDuck::Display(){ return "I'm a rubber duck";}/************************************************************************//* test.cpp *//************************************************************************//** * @file test.cpp * @brief Strategy模式的实现代码 * @author [e-mail] * http://blog.csdn.net/rabbit729* @version 1.0 * @date 2009-02-23 */ #include "Strategy.h"#include <iostream>using namespace std;void main(void){ Duck* duck = new MallardDuck(); cout<<duck->PerformQuack()<<endl; cout<<duck->PerformFly()<<endl; duck->SetFly(new FlyRocketPowered()); cout<<duck->PerformFly()<<endl;}

程序输出：

Quack
I'm flying!!
I'm flying with a rocket!
请按任意键继续. . .