策略（Strategy)模式，是比较简单的一种设计模式，但它的应用却随处可见。下面模拟游戏中常用的打斗场面，来理解策略模式。在游戏中，通常有n个角色，每个角色都能发出动作：fight。每个角色都使用不同的武器，并且可以更换武器。下面是此场景简化的C++实现：
Strategy.h
#ifndef _STRETEGY_H_#define _STRETEGY_H_//定义武器接口class WeaponBehavior
{
public: void virtual useWeapon() = 0;
};class Sword:public WeaponBehavior{public: void useWeapon();};class Axe:public WeaponBehavior{public: void useWeapon();};class Arrow:public WeaponBehavior{public: void useWeapon();};class Knife:public WeaponBehavior{public: void useWeapon();};//定义角色接口class Character{public: Character()
{ weapon = 0;
} void setWeapon(WeaponBehavior *w) { this->weapon = w; } void virtual fight() = 0;protected: WeaponBehavior *weapon;};class King:public Character{public: void fight();};class Queen:public Character{public: void fight();};class Knight:public Character{public: void fight();};class Troll:public Character{public: void fight();};#endif说明：
1.因为每个武器的使用方式不同，所以将使用武器的行为封装成接口，利用此接口调用具体武器的useWeapon行为。
2.因为每个角色都有打斗，更换武器的行为，各个角色的打斗行为不同，而更换武器的行为相同，所以将setWeapon在Character中实现，而打斗行为在各个具体的角色中实现。
Strategy.cpp
#include <iostream>#include "Strategy.h"using namespace std;void Sword::useWeapon(){ cout << "Use Sword to stuck!" << endl;}void Axe::useWeapon(){ cout << "Use Axe to chop!" << endl;}void Knife::useWeapon(){ cout << "Use Knife to kill!" << endl;}void Arrow::useWeapon(){ cout << "Use arrow!" << endl;}void King::fight(){ cout << "The king:" ; if ( this->weapon == NULL) { cout << "You don't have a weapon! Please Set Weapon!" << endl; } else { weapon->useWeapon(); }}void Queen::fight(){ cout << "The Queen:" ; if ( this->weapon == NULL) { cout << "You don't have a weapon! Please Set Weapon!" << endl; } else { weapon->useWeapon(); }}void Knight::fight(){ cout << "The Knight:" ; if ( this->weapon == NULL) { cout << "You don't have a weapon! Please Set Weapon!" << endl; } else { weapon->useWeapon(); }}void Troll::fight(){ cout << "The Troll:"; if ( this->weapon == NULL) { cout << "You don't have a weapon! Please Set Weapon!" << endl; } else { weapon->useWeapon(); }}main.cpp
#include <iostream>#include "Strategy.h"using namespace std;int main(){ //声明武器 WeaponBehavior *sw = new Sword();//声明剑 WeaponBehavior *axe = new Axe();//声明斧头 WeaponBehavior *arr = new Arrow();//声明弓箭 WeaponBehavior *kn = new Knife();//声明刀 //声明角色 Character *kin = new King(); Character *qu = new Queen(); Character *kni = new Knight(); Character *tr = new Troll(); //调用打斗行为 kin->fight(); qu->fight(); kni->fight(); tr->fight(); cout << endl; //更换武器 kin->setWeapon(sw); kin->fight(); cout << endl; kin->setWeapon(arr); kin->fight(); return 0;}策略(Strategy)模式体现了2个重要的面向对象设计原则：
1.封装变化。
2.针对接口编程。
原文链接: https://www.cnblogs.com/kex1n/archive/2012/02/02/2335898.html
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