Q_D和Q_Q的思考，问题来了“##”是什么含义呢？ [复制链接]

#define Q_DECLARE_PRIVATE(Class) \
    inline Class##Private* d_func() { return reinterpret_cast<Class##Private *>(d_ptr); } \
    inline const Class##Private* d_func() const { return reinterpret_cast<const Class##Private *>(d_ptr); } \
    friend class Class##Private;

#define Q_DECLARE_PRIVATE_D(Dptr, Class) \
    inline Class##Private* d_func() { return reinterpret_cast<Class##Private *>(Dptr); } \
    inline const Class##Private* d_func() const { return reinterpret_cast<const Class##Private *>(Dptr); } \
    friend class Class##Private;

#define Q_DECLARE_PUBLIC(Class)                                    \
    inline Class* q_func() { return static_cast<Class *>(q_ptr); } \
    inline const Class* q_func() const { return static_cast<const Class *>(q_ptr); } \
    friend class Class;

#define Q_D(Class) Class##Private * const d = d_func()
#define Q_Q(Class) Class * const q = q_func()

##是宏定义中用来做字符串连接的符号

举个例子，你看Qt源码会发现它使用的一些私有的类，都屁股后边加了private，就打这来的

再举个例子：
#define SHOWME(name) (cout<<myname##name<<endl);
......
main()
{
    string mynameyy="my name is : yy";
    SHOWME("yy")    ;    //equal to cout<<mynameyy<<endl;
    int mynamexx=100;
    SHOWME("xx");        //equal to cout<<mynamexx<<endl;
}