Custom STL container wrapper report weird compiler error

I have a C++ library (with over 50 source files) which uses a lot of STL routines with primary containers being list and vector. This has caused a huge code bloat and I would like to reduce the code bloat by creating another library which is essentially a wrapper over the list and vector.

I basically need a wrapper around std::list which works perfectly for the list container of any type.

Shown below is my list wrapper class.

template<typename T>
class wlist
{
private:
    std::list<T> m_list;

public:

    wlist();

    typedef std::list<void*>::iterator Iterator;
    typedef std::list<void*>::const_iterator CIterator;

    unsigned int size () { return m_list.size(); }
    bool empty () { return m_list.empty(); }
    void pop_back () { m_list.pop_back(); }
    void pop_front () { m_list.pop_front(); }
    void push_front (const T& item) { m_list.push_front(item); }
    void push_back (const T& item) { m_list.push_back(item); }
    bool delete_item (void* item);
    T& back () { return (m_list.empty()) ? NULL : m_list.back();}
    T& front () { return (m_list.empty()) ? NULL : m_list.front();}
    Iterator erase() { return m_list.erase(); }
    Iterator begin() { return (Iterator) m_list.begin(); }
    Iterator end() { return (Iterator) m_list.end(); }
};

File1.h:

cla开发者_开发问答ss label{

public:
int getPosition(void);
setPosition(int x);

private:
wlist<text> _elementText; // used in place of list<text> _elementText;

}

File2.h:

class image {

private:

    void draw image() {
        //Used instead of list<label*>::iterator currentElement = _elementText.begin();
        wlist<label*>::iterator currentElement = _elementText.begin();
        currentElement->getPosition(); // Here is the problem.     
        currentElement ++;
    }
}

Invoking getPosition() bombs with the following error message:

error: request for member `getPosition' in `*(&currentElement)->std::_List_iterator<_Tp>::operator-> [with _Tp = void*]()', which is of non-class type `void*'

Type casting getPosition() to label type didn't work. Additionally my iterators are of type void*.

---

I think the problem is that the line

currentElement->getPosition();

won't work because currentElement is an iterator over void*s, not labels. Since iterators over some type T act like T*s, this means that your currentElement iterator acts like a label**, and so writing the above code is similar to writing

(*currentElement).getPosition();

Here, the problem should be a bit easier to see - *currentElement is a label*, not a label, and so you can't use the dot operator on it.

To fix this, trying changing this code to

((label *)(*currentElement))->getPosition();

This dereferences the iterator and typecasts the void* to get a label*, then uses the arrow operator to call the getPosition() function on the label being pointed at.

---

Your iterator types seem to be declared in terms of std::list<void*>::iterator. This doesn't sound right to me...