Pass function point from child class to parent class

[jimhce]

Hi,

How can a child class passes its non-static member function to the parent class?

class A
{
public:
typedef void *(*object_t)(void *);
   A(object_t f) : func(f) {}
   virtual ~A(){}
private:
  object_t func;
};
 
class B : public A
{
public:
   B() : A(myFunc){}
   ~B(){}
   void *myFunc(void *){}
};
 

There was a compilation error of B() : A(&myFunc){}, unless the myFunc is to be a static member. How can do it without make myFunc be a static member?

Also, how can make the pthread_create to take a non-static member in class A? It was an error as well.

Thank you.

Jim

[weaknessforcats]

Use the Hollywood Principle (don't call us, we'll call you).

In this case, declare a private virtual function in the base class that is overridden by the derived classs.

Then when you create a derived object and access it as a base object you can call the base class virtual function which is really a call to the derived class virtual function giving you access to the derived data members.

This is part of the design pattern called Template Method.

[jimhce]

But the main problem here is that the non-static member function cannot be used by the pthread_create. I have to use a static member in the child class to allow the pthread_create to accept the function. The static cannot be used together with the virtual keyword. If I could find a way to allow pthread_create to accept a non-static member function, all the problem would resolved.

Thank you.

Jim

[RRick]

As for pthread, since its a C API, it won't be able to interpret or understand a non-static method from the class.

To get your class called by pthread you need to supply pthread_create with a static callback method from the class and pass the C++ object as the void * data. Pthread will call your static callback method with the object data. The static method reinterprets the void * data as the object and then you can call any method in the object.