Cocos2d-X学习之Ref类

先看看定义该类的头文件——CCRef.h

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 #ifndef __CCREF_H__
 #define __CCREF_H__

 #include "CCPlatformMacros.h"
 #include "ccConfig.h"

 NS_CC_BEGIN

 /**
  * @addtogroup base_nodes
  * @{
  */

 class Ref;

 /** Interface that defines how to clone an Ref */
 class CC_DLL Clonable
 {
 public:
     /** returns a copy of the Ref */
     virtual Clonable* clone() const = ;
     /**
      * @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;
     }
 };

 class CC_DLL Ref
 {
 public:
     /**
      * Retains the ownership.
      *
      * This increases the Ref's reference count.
      *
      * @see release, autorelease
      * @js NA
      */
     void retain();

     /**
      * Release 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();

     /**
      * Release 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;

 #if CC_ENABLE_SCRIPT_BINDING
 public:
     /// object id, ScriptSupport need public _ID
     unsigned int        _ID;
     /// Lua reference id
     int                 _luaID;
 #endif
 };

 class Node;

 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)

 // end of base_nodes group
 /// @}

 NS_CC_END

 #endif // __CCREF_H__

CCRef.h

头文件中主要有以下内容：

　　1、Clonable接口的定义；

　　2、Ref类的定义；

　　3、六个回调函数宏定义（包括相应类型定义）；

Clonable接口成员如下：

由接口的名称含义就可以知道，该接口的主要作用就是克隆Ref类的成员，由于该头文件之前还未有Ref类的定义，而接口函数中有使用了Ref，所以又一个Ref类的前向引用（C++好像有这么个概念）

clone()和copy()均可以完成Ref对象的克隆，不过新版本中copy()已经废弃，建议使用clone();

Ref类的函数成员如下：

retain()；每调用一次引用次数+1；

release()；每调用一次引用次数-1；

getReferenceCount()；获取引用的次数；

autorelease()；每调用一次autorelease pool 中的Ref引用数-1；

Ref类的数据成员中，有一个无符号整型成员 _referenceCount，用来记录引用次数的；

值得注意的是Ref类还有一个友元类AutoreleasePool；

回调函数及相应类型定义

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)

关于回调函数宏定义及类型定义，下篇中会详细说明，因为引擎中涉及到太多太多，而且还不是很好理解。