cocos2dx进阶学习之CCObject

继承关系

CCObject -> CCCopying

类定义

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;
};

成员解释

变量

unsigned int m_uID;

对象ID，由CCObject管理的全局唯一对象ID，用于CCScriptSupport类。每生成一个CCObject或者其子类对象，id自动增长1。

int m_nLuaID;

LuaID，从名字上看就知道是Lua脚本使用的ID，该ID由CCObject定义，但是CCObject并不管理该ID，由LuaCocos2d模块使用。

unsigned int m_uReference;

对象计数器，构造时为1，当调用对象的release成员函数时，这个值将自减，如果减少到0，那么对象被自己删除。

unsigned int m_uAutoReleaseCount;

调用autorelease的次数记录，初始化为0，调用一次自增1，用于析构函数检查是否需要从对象池中清除自身。

函数

CCObject(void);

构造函数，主要的功能是将成员函数初始化。

构造函数实现中，用一个静态变量来管理m_uID。

CCObject::CCObject(void)
: m_nLuaID(0)
, m_uReference(1) // when the object is created, the reference count of it is 1
, m_uAutoReleaseCount(0)
{
    static unsigned int uObjectCount = 0;

    m_uID = ++uObjectCount;
}

virtual ~CCObject(void);

析构函数，主要的功能是清除该对象与对象池、脚本对象管理之间的关系

CCObject::~CCObject(void)
{
    // if the object is managed, we should remove it
    // from pool manager
    if (m_uAutoReleaseCount > 0)
    {
        CCPoolManager::sharedPoolManager()->removeObject(this);
    }

    // if the object is referenced by Lua engine, remove it
    if (m_nLuaID)
    {
        CCScriptEngineManager::sharedManager()->getScriptEngine()->removeScriptObjectByCCObject(this);
    }
    else
    {
        CCScriptEngineProtocol* pEngine = CCScriptEngineManager::sharedManager()->getScriptEngine();
        if (pEngine != NULL && pEngine->getScriptType() == kScriptTypeJavascript)
        {
            pEngine->removeScriptObjectByCCObject(this);
        }
    }
}

void release(void);

release函数被调用时，计数器减一，如果计数器到0，那么

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

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

void retain(void);

增加计数器，保证对象不被删除

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

    ++m_uReference;
}

CCObject* autorelease(void);

让对象池管理器管理本对象，这样程序员可以不用去delete该对象内存

CCObject* CCObject::autorelease(void)
{
    CCPoolManager::sharedPoolManager()->addObject(this);
    return this;
}

CCObject* copy(void);

对象拷贝，这里调用了CCCopying的copyWithZone，那么copy也是和CCCopying一样没有做任何事情，拷贝工作还是需要子类做具体的实现，这里只是留有接口罢了

CCObject* CCObject::copy()
{
    return copyWithZone(0);
}

bool isSingleReference(void) const;

这个函数只是简单判断m_uReference是否为1而已

bool CCObject::isSingleReference(void) const
{
    return m_uReference == 1;
}

unsigned int retainCount(void) const;

返回引用个数

unsigned int CCObject::retainCount(void) const
{
    return m_uReference;
}

virtual bool isEqual(const CCObject* pObject);

判断是否相等

bool CCObject::isEqual(const CCObject *pObject)
{
    return this == pObject;
}

virtual void acceptVisitor(CCDataVisitor& visitor);

接受一个CCDataVisitor，可以通过该接口实现序列化等工作

void CCObject::acceptVisitor(CCDataVisitor &visitor)
{
    visitor.visitObject(this);
}

virtual void update(float dt) ;

更新函数，CCObject没有实现，只是预留接口

virtual void update(float dt) {CC_UNUSED_PARAM(dt);};

其他非成员相关

typedef void (CCObject::*SEL_SCHEDULE)(float);
typedef void (CCObject::*SEL_CallFunc)();
typedef void (CCObject::*SEL_CallFuncN)(CCNode*);
typedef void (CCObject::*SEL_CallFuncND)(CCNode*, void*);
typedef void (CCObject::*SEL_CallFuncO)(CCObject*);
typedef void (CCObject::*SEL_MenuHandler)(CCObject*);
typedef void (CCObject::*SEL_EventHandler)(CCEvent*);
typedef int (CCObject::*SEL_Compare)(CCObject*);

#define schedule_selector(_SELECTOR) (SEL_SCHEDULE)(&_SELECTOR)
#define callfunc_selector(_SELECTOR) (SEL_CallFunc)(&_SELECTOR)
#define callfuncN_selector(_SELECTOR) (SEL_CallFuncN)(&_SELECTOR)
#define callfuncND_selector(_SELECTOR) (SEL_CallFuncND)(&_SELECTOR)
#define callfuncO_selector(_SELECTOR) (SEL_CallFuncO)(&_SELECTOR)
#define menu_selector(_SELECTOR) (SEL_MenuHandler)(&_SELECTOR)
#define event_selector(_SELECTOR) (SEL_EventHandler)(&_SELECTOR)
#define compare_selector(_SELECTOR) (SEL_Compare)(&_SELECTOR)

以上宏，定义成员函数指针类型，用于schedule回调指针

总结

CCObject作为cocos2dx中大部分类的父类，提供了

1）内存管理功能

2）为脚本提供对象ID管理

3）序列化接口

4）提供update接口