标签：des style color io os 使用 ar java for
【名词解释】Ref类实现了引用计数的功能，它是引擎代码中绝大多数其他类的父类，定义在CCRef.h中，实现在CCRef.cpp中。其实在CCRef.h文件中不止定义了Ref类，还定义了Clonable类、一系列的宏定义和类型定义，不过我们暂且将精力放在Ref类的解读上。Ref类使用私有成员变量_referenceCount保存计数值，并通过retain，release和autorelease函数实现增减计数值。
<span style="font-family:Microsoft YaHei;font-size:18px;">class CC_DLL Ref
{
public:
/**
* Retains the ownership.
*
* This increases the Ref's reference count.
*
* @see release, autorelease
* @js NA
*/
void retain();
/**
* Releases the ownership immediately.
*
* This decrements the Ref's reference count.
*
* If the reference count reaches 0 after the descrement, this Ref is
* destructed.
*
* @see retain, autorelease
* @js NA
*/
void release();
/**
* Releases the ownership sometime soon automatically.
*
* This descrements the Ref's reference count at the end of current
* autorelease pool block.
*
* If the reference count reaches 0 after the descrement, this Ref is
* destructed.
*
* @returns The Ref itself.
*
* @see AutoreleasePool, retain, release
* @js NA
* @lua NA
*/
Ref* autorelease();
/**
* Returns the Ref's current reference count.
*
* @returns The Ref's reference count.
* @js NA
*/
unsigned int getReferenceCount() const;
protected:
/**
* Constructor
*
* The Ref's reference count is 1 after construction.
* @js NA
*/
Ref();
public:
/**
* @js NA
* @lua NA
*/
virtual ~Ref();
protected:
/// count of references
unsigned int _referenceCount;
friend class AutoreleasePool;
};</span>Ref将构造函数声明为保护类型，防止直接生成Ref对象，在构造函数的成员初始化列表中将引用计数值_referenceCount初始化为1。retain函数将_referenceCount加1，release函数则减1，autorelease函数则将对象托管给AutoreleasePool对象进行管理，具体实现代码如下：
<span style="font-family:Microsoft YaHei;font-size:18px;">NS_CC_BEGIN
Ref::Ref() : _referenceCount(1) // when the Ref is created, the reference count of it is 1
{
}
Ref::~Ref()
{
}
void Ref::retain()
{
CCASSERT(_referenceCount > 0, "reference count should greater than 0");
++_referenceCount;
}
void Ref::release()
{
CCASSERT(_referenceCount > 0, "reference count should greater than 0");
--_referenceCount;
if (_referenceCount == 0)
{
delete this;
}
}
Ref* Ref::autorelease()
{
PoolManager::getInstance()->getCurrentPool()->addObject(this);
return this;
}
unsigned int Ref::getReferenceCount() const
{
return _referenceCount;
}
NS_CC_END</span>【Clonable类的定义】
<span style="font-family:Microsoft YaHei;font-size:18px;">/** Interface that defines how to clone an Ref */
class CC_DLL Clonable
{
public:
/** returns a copy of the Ref */
virtual Clonable* clone() const = 0;
/**
* @js NA
* @lua NA
*/
virtual ~Clonable() {};
/** returns a copy of the Ref.
* @deprecated Use clone() instead
*/
CC_DEPRECATED_ATTRIBUTE Ref* copy() const
{
// use "clone" instead
CC_ASSERT(false);
return nullptr;
}
};</span>【回调函数的定义】
<span style="font-family:Microsoft YaHei;font-size:18px;">typedef void (Ref::*SEL_CallFunc)(); typedef void (Ref::*SEL_CallFuncN)(Node*); typedef void (Ref::*SEL_CallFuncND)(Node*, void*); typedef void (Ref::*SEL_CallFuncO)(Ref*); typedef void (Ref::*SEL_MenuHandler)(Ref*); typedef void (Ref::*SEL_SCHEDULE)(float); #define callfunc_selector(_SELECTOR) static_cast<cocos2d::SEL_CallFunc>(&_SELECTOR) #define callfuncN_selector(_SELECTOR) static_cast<cocos2d::SEL_CallFuncN>(&_SELECTOR) #define callfuncND_selector(_SELECTOR) static_cast<cocos2d::SEL_CallFuncND>(&_SELECTOR) #define callfuncO_selector(_SELECTOR) static_cast<cocos2d::SEL_CallFuncO>(&_SELECTOR) #define menu_selector(_SELECTOR) static_cast<cocos2d::SEL_MenuHandler>(&_SELECTOR) #define schedule_selector(_SELECTOR) static_cast<cocos2d::SEL_SCHEDULE>(&_SELECTOR)</span>上面回调函数的定义分为两步：类型定义和宏定义。我们以SEL_CallFuncO为例进行说明，首先通过typedef类型定义了一个成员函数指针SEL_CallFuncO，SEL_CallFuncO是Ref类的成员，同时接收Ref类型的指针形参：
<span style="font-family:Microsoft YaHei;font-size:18px;">#define CC_USE_MEM_LEAK_DETECTION 0</span>
作为开关的。内存泄漏检测代码主要包括Ref类静态成员函数：
<span style="font-family:Microsoft YaHei;font-size:18px;">class CC_DLL Ref
{
// Memory leak diagnostic data (only included when CC_USE_MEM_LEAK_DETECTION is defined and its value isn't zero)
#if CC_USE_MEM_LEAK_DETECTION
public:
static void printLeaks();
#endif
};</span>
定义在CCRef.cpp文件内的静态函数（静态函数与普通函数不同之处在于，它只在声明它的文件中可见，其他文件不可见，同时，其他文件中可以定义相同名字的函数，不会发生冲突）
#if CC_USE_MEM_LEAK_DETECTION static void trackRef(Ref* ref); static void untrackRef(Ref* ref); #endiftrackRef函数在Ref类对象创建的时候调用，untrackRef在Ref类对象销毁的时候调用，Ref对象实例保存在静态链表__refAllocationList中，实现代码如下所示：
#if CC_USE_MEM_LEAK_DETECTION
static std::list<Ref*> __refAllocationList;
void Ref::printLeaks()
{
// Dump Ref object memory leaks
if (__refAllocationList.empty())
{
log("[memory] All Ref objects successfully cleaned up (no leaks detected).\n");
}
else
{
log("[memory] WARNING: %d Ref objects still active in memory.\n", (int)__refAllocationList.size());
for (const auto& ref : __refAllocationList)
{
CC_ASSERT(ref);
const char* type = typeid(*ref).name();
log("[memory] LEAK: Ref object '%s' still active with reference count %d.\n", (type ? type : ""), ref->getReferenceCount());
}
}
}
static void trackRef(Ref* ref)
{
CCASSERT(ref, "Invalid parameter, ref should not be null!");
// Create memory allocation record.
__refAllocationList.push_back(ref);
}
static void untrackRef(Ref* ref)
{
auto iter = std::find(__refAllocationList.begin(), __refAllocationList.end(), ref);
if (iter == __refAllocationList.end())
{
log("[memory] CORRUPTION: Attempting to free (%s) with invalid ref tracking record.\n", typeid(*ref).name());
return;
}
__refAllocationList.erase(iter);
}
#endif // #if CC_USE_MEM_LEAK_DETECTION
［当我在研究Cocos-2dx的源码时，我在想什么］－Ref类，一切的起源
标签：des style color io os 使用 ar java for
原文地址：http://blog.csdn.net/asce1885/article/details/39958963
