c++ - function pointer to a different class member -

i have following problem:

class { public:    a()    {}    int foo(int a)    {       return a;    } };  class b { private:    int (a::*pfoo)(int); public:    b(int (a::*_pfoo)(int))   {      this->pfoo = _pfoo;   }      int cfoo(int i)   {      this->pfoo(i); //this causes problem compiler says it's not pointer   } };  a; b b(&a::foo); 

i've tried already

int (*pfoo)(int) 

instead of

int (a::*pfoo)(int) 

but there problems constructor , when used b b(&a.foo) there compiler error says have use b b(&a::foo)

you trying call a:foo object of type b pointer member function of a requires instance of a.

instead of saving pointer or reference a inside b can redesign code b little more generic:

#include <functional> struct {   int foo(int a)   {     return a;   } };  class b { private:   std::function<int(int)> pfoo; public:   b(std::function<int(int)> foofunc)      : pfoo(foofunc) { }   int cfoo(int i)   {     return pfoo(i);    } }; 

now b can take function pointer returning int 1 int argument , can bind function pointer a::foo instance of a:

a my_a; b my_b(std::bind(&a::foo, my_a, std::placeholders::_1));  my_b.cfoo(2); // works 

see on ideone.