c++ - 单例中的 FunktionPointerArray

Question

我尝试在拥有线程的单例中实现函数指针数组。在线程函数中我得到一个错误，告诉我一个成员必须相对于一个对象。更多内容在评论区...

标题:

typedef struct{
  int action;
  HWND handle;
}JOB;

class Class{
public:
  enum Action { 1,2 };

private:
  JOB    m_currentJob;
  queue<JOB> Jobs;

  static DWORD WINAPI ThreadFunction(LPVOID lpParam);

  void (Class::*ftnptr[2])(JOB Job);
  void Class::ftn1(JOB Job);
  void Class::ftn2(JOB Job);

// Singleton pattern
public:
  static Class*  getInstance(){
    if(sInstance == NULL)
      sInstance = new Class();
    return sInstance;
  }
private:
  Class(void);
  ~Class(void);
  static Class*  sInstance;
};

正文:

#include "Class.h"

Class* Class::sInstance = NULL;

Class::Class(){
  this->ftnptr[0] = &Class::ftn1;
  this->ftnptr[1] = &Class::ftn2;
}

DWORD WINAPI Class::AutoplayerThreadFunction(LPVOID lpParam)
{  
  Class *pParent = static_cast<Class*>(lpParam);

  while(true){
   (pParent->*ftnptr[pParent->m_currentJob.action])(pParent->m_currentJob);
   /* The line above causes the compiler error. Curious to me is that 
    * neither "pParent->m_currentJob" nor "pParent->m_currentJob" cause 
    * any problems, although they are members too like the ftnptr array.
    */
  }
}

void Class::ftn1(JOB Job){}
void Class::ftn2(JOB Job){}

通过 getInstance 从 SingletonPattern 调用并没有使它变得更好。有什么建议吗？

Answer 1

ftnptr 是类的成员。但是，您可以直接访问它。也就是说，pParent->*ftnptr[...] 表示“访问指针 ftnptr[...] 指定的 pParent 成员”，但并不意味着 ftnptr 也是 pParent 的成员。

正确的代码是 (pParent->*(pParent->ftnptr[...]))(...)。但我建议从中提取数组索引表达式:

auto fnptr = pParent->ftnptr[...];
(pParent->*fnptr)(...);