iterating getters of a vector of pointers - c++

Question

I am trying to write an iterator class which returns a getter function return value when it is dereferenced. The code works fine, my only problem is that I would like to write the member_ptr_functor using only one template parameter and not 3, since I am supposed to be able to deduce the types of the argument and return value from the member function type. I think the problematic one is the argument type, I tried using boost::remove_ptr&, but I couldn't compile it.
#include <iostream>
#include <vector>
#include <boost/iterator/transform_iterator.hpp>
#include <boost/iterator/indirect_iterator.hpp>
using namespace boost;
using namespace std;
class CTest
{
private:
int m_x;
public:
CTest(int x) : m_x(x)
{
}
const int& GetX() const
{
return m_x;
}
};
template<typename MemFunType, typename ArgumentType, typename ResultType>
class member_ptr_functor : public unary_function<ArgumentType, ResultType>
{
private:
MemFunType m_MemFun;
public:
typedef ArgumentType argument_type;
typedef ResultType result_type;
member_ptr_functor(MemFunType MemFun) : m_MemFun(MemFun)
{
}
result_type operator() (argument_type arg) const
{
return m_MemFun(&arg);
}
};
template<typename MemFunType, typename ArgumentType, typename ResultType>
member_ptr_functor<MemFunType, ArgumentType, ResultType> make_member_ptr_functor(MemFunType MemFun)
{
return member_ptr_functor<MemFunType, ArgumentType, ResultType>(MemFun);
}
class CPrintFunctor : public unary_function<int, void>
{
public:
void operator() (const int n) const
{
cout << n << endl;
}
};
int main()
{
typedef vector<CTest> Container_t;
Container_t v;
v.push_back(CTest(1));
CPrintFunctor PF;
Container_t::const_iterator itStart = v.begin();
Container_t::const_iterator itEnd = v.end();
typedef member_ptr_functor<const_mem_fun_t<const int&, CTest> , CTest, const int&> member_ptr_functor_t;
member_ptr_functor_t MemberPtrFunctor = member_ptr_functor_t(mem_fun(&CTest::GetX));
typedef transform_iterator<member_ptr_functor_t, Container_t::const_iterator, const int&, const int> transform_iterator_t;
transform_iterator_t itTransformStart = make_transform_iterator(itStart, MemberPtrFunctor);
transform_iterator_t itTransformEnd = make_transform_iterator(itEnd, MemberPtrFunctor);
for_each(itTransformStart, itTransformEnd, PF);
return 0;
}
Hagai.

Answer 1

This does not answer your question directly but rather suggests alternative approach.
You are already using Boost, so why do you not take it one step further, use Boost.Range:
#include <boost/functional.hpp>
#include <boost/range.hpp>
#include <boost/range/algorithm/for_each.hpp>
#include <boost/range/adaptor/transformed.hpp>
// ...
int main ()
{
// ...
boost::range::for_each (
boost::adaptors::transform (v, boost::mem_fun_ref (&CTest::GetX)),
PF);
}
This lets you write the functionality that you want without having to define own functors and without using too many typedefs.