pointing a variable to a member function outside a class

[wilintec]

Hello, my question is this.
In C++, how do i call a method member of class A from a class B, using a pointer.
By the way Class A and B are of different types.

I read that when a pointer is pointing to member function it can only point member functions within the class. But how can i point to a member function outside the class.?????



for example

class A
{
public:

int add(int x) {

return x+x;
}
};
int main()

{

typedef int (A::*pointer)() ;
pointer func = &A::add;
A objt;
B objt2;

obt2.*func(2);// the compiler give me an error of incompatible with object type ‘B’


return 0;
}

[weaknessforcats]

If you are in class A and need to call a method on class B then a class B object (or a pointer to it) must be a member variable of class A:

class A
{
   public:
     void MethodA();
   private:
   B obj;
};

or

class A
{
    public:
     void MethodA();
   private:
   B* ptr;
};

Then in your code for A::MethodA():

void A::MethodA()
{
    obj.MethodB();
  //or if you have the address of a B object.
    ptr->MethodB();
}

Then your main():

int main()
{
   A obj;  
   obj.MethodA();
}

Of course, other member functions of A (like the constructors) must take care of either creating the B object or getting the address of it.