Cocos2dx 内存管理机制

1.引用计数机制

要了解cocos2dx引用计数的机制，首先我们来看看CCObject这个类

class CC_DLL CCObject : public CCCopying
{
public:
    // object id, CCScriptSupport need public m_uID
    unsigned int        m_uID;
    // Lua reference id
    int                 m_nLuaID;
protected:
    // count of references
    unsigned int        m_uReference;
    // count of autorelease
    unsigned int        m_uAutoReleaseCount;
public:
    CCObject(void);
    /**
     *  @lua NA
     */
    virtual ~CCObject(void);
    
    void release(void);
    void retain(void);
    CCObject* autorelease(void);
    CCObject* copy(void);
    bool isSingleReference(void) const;
    unsigned int retainCount(void) const;
    virtual bool isEqual(const CCObject* pObject);

    virtual void acceptVisitor(CCDataVisitor &visitor);

    virtual void update(float dt) {CC_UNUSED_PARAM(dt);};
    
    friend class CCAutoreleasePool;
};

● 当m_uReference=0时会自动释放该对象，每引用一次对象的时候，m_uReference会+1，当object被创建，会初始化为1.

● 当m_uAutoReleaseCount !=0时表示该对象自动释放（autorelease）。

●void retain(void) 对m_uReference+1操作,可以防止对象被释放

●retainCount() 返回m_uReference值

● 跟踪一下void release()方法，我们会发现是对引用计数m_uReference进行-1操作，为0时删除对象

void CCObject::release(void)
{
    CCAssert(m_uReference > 0, "reference count should greater than 0");
    --m_uReference;

    if (m_uReference == 0)
    {
        delete this;
    }
}

2.使用引用计数手动管理内存

因此，如果我们想手动来管理内存的释放，我们可以使用这样子，

        CCSprite* sprite1=new CCSprite();
	sprite1->initWithFile("CloseNormal.png");
	CCLOG("sprite1 retain:%d",sprite1->retainCount());//sprite1 retain:1
	this->addChild(sprite1);         //addChild会对引用计数+1，可以跟踪看一下，最后会对object->retain()操作
	CCLOG("sprite1 retain:%d",sprite1->retainCount());//sprite1 retain:2
	sprite1->release();
	CCLOG("sprite1 retain:%d",sprite1->retainCount());//sprite1 retain:1
	this->removeChild(sprite1);    //对m_uReference进行-1,跟踪一下会发现对object进行CC_SAFE_RELEASE()安全释放操作
	CCLOG("sprite1 retain:%d",sprite1->retainCount());//sprite1 retain:-17891602

3.自动管理autorelease

还记得helloWorld里面怎么创建一个Sprite吗？

CCSprite* pSprite = CCSprite::create("HelloWorld.png");

跟踪CCSprite::create()

CCSprite* CCSprite::create(const char *pszFileName)
{
    CCSprite *pobSprite = new CCSprite();
    if (pobSprite && pobSprite->initWithFile(pszFileName))
    {
        pobSprite->autorelease();
        return pobSprite;
    }
    CC_SAFE_DELETE(pobSprite);
    return NULL;
}