Using a member function pointer within a class

Question

Given an example class:

class Fred
{
public:
Fred() 
{
    func = &Fred::fa;
}

void run()
{
     int foo, bar;
     *func(foo,bar);
}

double fa(int x,          


        

Answer 1

There are two things you need to take care of. First is the declaration of the function pointer type:

private:
  typedef double (Fred::*fptr)(int x, int y);
  fptr func;

Next is the syntax for calling the function using a pointer:

(this->*func)(foo,bar)

Here is the modified sample code that will compile and run:

#include 

class Fred
{
public:
  Fred() 
  {
    func = &Fred::fa;
  }

  void run()
  {
    int foo = 10, bar = 20;
    std::cout << (this->*func)(foo,bar) << '\n';
  }

  double fa(int x, int y)
  {
    return (double)(x + y);
  }
  double fb(int x, int y)
  {
  }

private:
  typedef double (Fred::*fptr)(int x, int y);
  fptr func;
};

int
main ()
{
  Fred f;
  f.run();
  return 0;
}