Cocos2dx学习笔记(一)、Ref类

在Cocos2dx中，所有的对象基本上都继承 Ref类或者 Ref和Clonable，首先看看 ref类的定义

class CC_DLL Ref
{
public:

<span style="white-space:pre"> </span>//计数加1
    void retain();
    
<span style="white-space:pre"> </span>//计数减1，如果为0，删除对象
    void release();

<span style="white-space:pre"> </span>//添加到对象池中，别忘了PoolManager（对象池管理器） 管理AutoreleasePool（对象池），AutoreleasePool管理Ref
    Ref* autorelease();

<span style="white-space:pre"> </span>//得到当前的计数
    unsigned int getReferenceCount() const;
    
protected:
    
<span style="white-space:pre"> </span>//创建时计数设为1
    Ref();
    
public:
 
    virtual ~Ref();
    
protected:
    /// count of references
<span style="white-space:pre"> </span>//计数变量
    unsigned int _referenceCount;
    
<span style="white-space:pre"> </span>//友元类
    friend class AutoreleasePool;
    
#if CC_ENABLE_SCRIPT_BINDING
public:
    /// object id, ScriptSupport need public _ID
    unsigned int        _ID;
    /// Lua reference id
    int                 _luaID;
#endif
};
首先看 构造函数 

Ref::Ref()
: _referenceCount(1)
{
#if CC_ENABLE_SCRIPT_BINDING
static unsigned int uObjectCount = 0;
_luaID = 0;
_ID = ++uObjectCount;
_scriptObject = nullptr;
#endif
#if CC_REF_LEAK_DETECTION
trackRef(this);
#endif
}

其中uObjectCount 为计数器, 记录多少对象继承 Ref类
void Ref::retain()
{
CCASSERT(_referenceCount > 0, "reference count should be greater than 0");
++_referenceCount;
}retain 函数为新建一个对象时候所使用的, 每次新建时候计数器加一

void Ref::release()
{
CCASSERT(_referenceCount > 0, "reference count should be greater than 0");
--_referenceCount;
if (_referenceCount == 0)
{
#if defined(COCOS2D_DEBUG) && (COCOS2D_DEBUG > 0)
auto poolManager = PoolManager::getInstance();
if (!poolManager->getCurrentPool()->isClearing() && poolManager->isObjectInPools(this))
{
CCASSERT(false, "The reference shouldn't be 0 because it is still in autorelease pool.");
}
#endif
#if CC_REF_LEAK_DETECTION
untrackRef(this);
#endif
delete this;
}
}release 为释放函数 ,释放一个对象的时候 计数器减去1