Question

When using the std::for_each,

class A; vector<A*> VectorOfAPointers;  std::for_each(VectorOfAPointers.begin(), VectorOfAPointers.end(), std::mem_fun(&A::foo)); 

If we have classes inheriting from A and implementing foo(), and we hold a vector of pointers to A, is there any way to call a polymorphic call on foo(), rather then explicitly calling A::foo()? Note: I can’t use boost, only standard STL.

Thanks, Gal

Answer 1

It actually works this way.

#include <algorithm> #include <iostream> #include <functional> #include <vector>  struct A {     virtual void foo() {         std::cout << 'A::foo()' << std::endl;     } }; struct B: public A {     virtual void foo() {         std::cout << 'B::foo()' << std::endl;     } };  int main() {     std::vector<A*> VectorOfAPointers;     VectorOfAPointers.push_back(new B());     std::for_each(VectorOfAPointers.begin(), VectorOfAPointers.end(), std::mem_fun(&A::foo));     return 0; } 

prints

B::foo() 

So it does exactly what you want. Check that virtual keywords are present though, it’s easy to forget them.