请教一个Strategy实现的问题

[rabbit729]

小弟使用如下代码实现了Strategy模式，感觉里面好像存在内存泄漏的情况，请各位高手帮忙分析一下，代码如下：
/***********Strategy.h******************/
// ***************************************************************
// Strategy version: 1.0 · date: 09/01/2008
// -------------------------------------------------------------

// -------------------------------------------------------------
// Copyright (C) 2008 - All Rights Reserved
// ***************************************************************

#ifndef STRATEGY_H_
#define STRATEGY_H_

class WeaponBehavior;

class Character
{
public:
Character();
Character(WeaponBehavior* pWeapon);

~Character();

void fight();
void SetWeapon(WeaponBehavior* w);

private:
WeaponBehavior* m_weapor;

};

class Queue : public Character
{
public:
Queue();
~Queue();
};

class King : public Character
{
public:
King();
~King();
};

class WeaponBehavior
{
public:
WeaponBehavior();
~WeaponBehavior();

virtual void useWeapon() = 0;
};

class KnifeBehvior : public WeaponBehavior
{
public:
KnifeBehvior();
~KnifeBehvior();

virtual void useWeapon();
};

class SwordBehavior : public WeaponBehavior
{
public:
SwordBehavior();
~SwordBehavior();

virtual void useWeapon();
};

#endif

/************Strategy.cpp********************/
#include "Strategy.h"
#include <iostream>

using namespace std;

Character::Character():m_weapor(NULL)
{

}

Character::Character(WeaponBehavior* pWeapon)
{
m_weapor = pWeapon;
}

Character::~Character()
{
if (m_weapor != NULL)
{
delete m_weapor;
m_weapor = NULL;
}
}

void Character::fight()
{
m_weapor->useWeapon();
}

void Character::SetWeapon(WeaponBehavior* w)
{
m_weapor = w;
}

Queue::Queue():Character(new KnifeBehvior())
{

}

Queue::~Queue()
{

}

King::King():Character(new SwordBehavior())
{

}

King::~King()
{

}

WeaponBehavior::WeaponBehavior()
{

}

WeaponBehavior::~WeaponBehavior()
{

}

KnifeBehvior::KnifeBehvior()
{

}

KnifeBehvior::~KnifeBehvior()
{

}

void KnifeBehvior::useWeapon()
{
cout<<"Fight use Knife!"<<endl;
}

SwordBehavior::SwordBehavior()
{

}

SwordBehavior::~SwordBehavior()
{

}

void SwordBehavior::useWeapon()
{
cout<<"Fight use Sword!"<<endl;
}

/*************Main.cpp*******************/
#include "Strategy.h"

void main()
{
Character* character = new King();
character->fight();

WeaponBehavior* pWeapon = new KnifeBehvior();
character->SetWeapon(pWeapon);
character->fight();

delete character;
character = 0;
}

上面代码在执行时不会出现问题，但是我感觉是不是得使用delete pWeapon;释放pWeapon，不过加上的话执行是弹出错误，请大家帮忙分析一下，上面代码是否存在内存泄漏，谢谢！

[e_sharp]

Character::~Character() //pWeapon 在这里释放 
{ 
	if (m_weapor != NULL) 
	{ 
		delete m_weapor; 
		m_weapor = NULL; 
	} 
} 

[冷月清晖]

无泄漏，同上，

所以无论你：先delete pWeapon;

再 delete character; 还是反过来
都会报错，因为虽然上面你做了m_weapor = NULL;
但是main中的变量还是有值，非空判断也失效。

[jeffchen]

[Quote=引用 3 楼 wuliang_227 的回复:]
目前看上去确实没有内存泄露，但如果这样用就有问题了：

C/C++ code
void main()
{
Character* character = new King();
character->fight();

WeaponBehavior* pWeapon = new KnifeBehvior();
character->SetWeapon(pWeapon);
character->fight();

WeaponBehavior* pAnotherWeapon = new SwordBehavior;
character->SetWeapon(pAnotherWeapon);

delete character;
character = 0;
}




本着谁new谁…
[/Quote]

我建议这样写：
C/C++ code
void Character::SetWeapon(WeaponBehavior* w)
{
if(m_weapor != NULL)
{
delete m_weapor;
m_weapor = NULL;
}

m_weapor = w;
}

void main()
{
Character* character = new King();
character->fight();

character->SetWeapon(new KnifeBehvior());
character->fight();

character->SetWeapon(new SwordBehavior());

delete character;
character = 0;
}

[wuliang_227]

目前看上去确实没有内存泄露，但如果这样用就有问题了：

void main()
{
Character* character = new King();
character->fight();

WeaponBehavior* pWeapon = new KnifeBehvior();
character->SetWeapon(pWeapon);
character->fight();

WeaponBehavior* pAnotherWeapon = new SwordBehavior;
character->SetWeapon(pAnotherWeapon);

delete character;
character = 0;
} 

本着谁new谁delete的原则，我认为 Character::SetWeapon 可以这样：

WeaponBehavior* Character::SetWeapon(WeaponBehavior* w)
{
    WeaponBehavior* pRetWeapor = NULL;
  
    if(m_weapor != w)
     {
        pRetWeapor = m_weapor;
        m_weapor = w;
     }

    return pRetWeapor;
}

void main()
{
Character* character = new King();
character->fight();

WeaponBehavior* pWeapon = new KnifeBehvior();
character->SetWeapon(pWeapon);
character->fight();

WeaponBehavior* pAnotherWeapon = new SwordBehavior;
WeaponBehavior* pNeedFreeWeapon = character->SetWeapon(pAnotherWeapon);
if(pNeedFreeWeapon)
{
   delete pNeedFreeWeapon;
   pNeedFreeWeapon = NULL;
}
delete character;
character = 0;
} 

[mxm324]

同上...不过在赋予行为的时候需要看你的这些行为会不会被其它character共享...因为其实很多时候并不需要每次替换一个行为就去new一个行为..用原来的也行..这个时候就要考虑delete问题了...

[gezichong]

这个文章：

http://www.cnblogs.com/chengy024/archive/2008/04/28/1175033.html

和LZ的一样

[wjzhang_1983]

jeffchen 正解

[changsheng230]

void main()
{
Character* character = new King();
character->fight();

WeaponBehavior* pWeapon = new KnifeBehvior();
character->SetWeapon(pWeapon);
character->fight();

WeaponBehavior* pAnotherWeapon = new SwordBehavior;
character->SetWeapon(pAnotherWeapon);

delete character;
character = 0;
} 

//用auto_ptr更好，只要别把指针穿来传去得:

void main()
{
std::auto_ptr<Character*> character(new King());
character->fight();
std::auto_ptr<WeaponBehavior*> pWeapon (new KnifeBehvior());
character->SetWeapon(pWeapon);
character->fight();
std::auto_ptr<WeaponBehavior*> pAnotherWeapon (new KnifeBehvior());

character->SetWeapon(pAnotherWeapon);
}