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 = 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;
    }
};

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__

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。