iterating getters of a vector of pointers

Question

Hi, 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.