Question

I am trying to transfer a function as a parameter to a different function.

for some reason it is not working.

//myClass.h
class MyClass
{
public:

typedef int (*MyClass::ptrToMember)(float, char);

  ptrToMember p1;
  MyClass::MyClass();
  void hello(ptrToMember fun);

  int SendIt (float a, char b); 

};



//MyClass.cpp
MyClass::MyClass(){
  p1 = &(MyClass::SendIt);
  hello(p1);

}
int MyClass::SendIt (float a, char b) 
{ 
  std::cout << "MyClass::SendIt "<<a<<std::endl; 

  return 1; 
}

void MyClass::hello(ptrToMember fun){

 int result = (*fun)(12, 'a');
  std::cout << result << std::endl;
}

would appreciate it, if someone can tell me what my mistake is.

Answer 1

typedef int (*MyClass::ptrToMember)(float, char);
             ^
// your mistake is here

Pointers to class member functions are declared like this:

typedef int (MyClass::*ptrToMember)(float, char);
                      ^

And called like this (test is the class instance – can also be ‘this’):

 (test.*pointer)(parameters) // if test is automatically allocated

or

 (test->*pointer)(parameters) // if test is a pointer

The decleration operator is ::*, while the operator to invoke your pointer to a member function are .* and ->*.

Edit:

This line:

p1 = &(MyClass::SendIt);

actually has to be:

p1 = &MyClass::SendIt; // without parentheses