c++ - 在 C++ 中访问派生类变量？

Question

我正在尝试访问派生类中的变量。

     printf("%c", God.m_Please.me);

在 God 类声明中，我已将 m_Please 声明为

     private:
     Please *m_Please

helpme 是在派生自 Please 的类中声明的变量

    class Help : public Please

而我被定义为

    unsigned char me[1000];

当我尝试编译时出现错误

error C2228: left of '.me' must have class/struct/union type

我正在使用 Visual Studio 6.0

请回复....

orward declare "class Please;"在上帝面前——wqking这有助于消除第一个错误 :) 但我仍然遇到其他 2 个错误

谢谢，

Answer 1

Please* Please 是私有(private)的。您不能从派生类访问私有(private)成员。它必须受到保护。

class Please{
  protected:
  Please* m_Please;
  int pplHelped;
};

class Help : public Please {

  void whatever(){
      //assume m_Please was initialized elsewhere
      Please::m_Please->pplHelped; //do something with pplHelped
  }
};

如果您试图通过派生类的实例访问基成员变量，则应在基类中将其声明为public。

class Please{
  public:
  Please* m_Please; //init this somewhere
  int pplHelped;
};

class Help : public Please{
};

void somefunc(){
  Help God;
  //assume m_Please was initialized in Constructor
  printf("%d\n", God.m_Please->pplHelped;
}