设计模式-行为-Strategy（策略）模式

Strategy（策略）模式与 Template 模式目的相同，区别在于实现手法：Template 依赖继承，而 Strategy 采用组合，从而解决了继承带来的弊端。

问题背景

为了在业务逻辑（算法）的具体实现与抽象接口之间实现解耦，Strategy 模式将算法（业务逻辑）封装到一个 Context 类中，通过组合的方式持有算法对象，再通过委托将抽象接口的调用转发给具体的组合对象。State 模式与之有类似的区别。

Strategy 模式定义了一系列算法并将它们封装起来，使各算法可以相互替换，从而让算法的变化独立于使用它的客户。

示例 1：基本策略模式

#include "PublicHeaders.h"

class Strategy
{
public:
	virtual void AlgrithmInterface() = 0;
};

class ConCreateStrategy :public Strategy
{
public:
	void AlgrithmInterface()override
	{
		cout << __FUNCTION__ << endl;
	}

};
class Contex
{
public:
	Contex(Strategy *strategy)
	{
		this->strategy = strategy;
	}

	void DoAction()
	{
		this->strategy->AlgrithmInterface();
	}
private:
	Strategy*strategy;
};


/**
 * @brief  test function for strategy pattern
 */
void testStrategy()
{
	Contex* contex = new Contex(new ConCreateStrategy);

	contex->DoAction();

}

示例 2：武器系统

class WeaponStrategy
	{
	public:
		virtual void doFire() = 0;
	};

	class GaTlingGun_Strategy :public WeaponStrategy
	{
	public:
		virtual void doFire()override
		{


		}

	};

	class PistolGun_Strategy :public WeaponStrategy
	{
	public:
		virtual void doFire()override
		{

		}

	};


	class PlayerContex
	{
	public:
		void Fire()
		{
			weapon->doFire();
		}


		void setWeapon(WeaponStrategy *strategy)
		{
			this->weapon = strategy;
		}

		WeaponStrategy*weapon;
	};

	void test()
	{
		PlayerContex*player = new PlayerContex;
		player->setWeapon(new GaTlingGun_Strategy);

		player->Fire();


	}