AW: [boost] boost::mpl create objects of types in a typelist

From: Sebastian Faust (sfaust_at_[hidden])
Date: 2003-11-15 19:47:52

Hi,

> What I now wanna, and I sadly don't know how to solve such, is the
> follwing:
>
> Given again the classes which I wanna create with some kind of special
> factory:
>
> class vehicle
> {
>     public:
>         vehicle(vehicle* successor) : m_successor(successor) {}
>         virtual vehicle* create(vehicle* successor) = 0;
>         vehicle* m_successor;
>
> };
>
> class car : public vehicle
> {
>     public:
>	    static const int _key = 1;         
>          virtual vehicle* create(vehicle* successor)
>          {
>             return new car(successor);
>          }
>};
>
> class bicycle : public vehicle
> {
>     public:
>	    static const int _key = 2;
>         virtual vehicle* create(vehicle* successor)
>         {
>             return new bicycle (successor);
>         }
> };
>
> Now the main-Function should look the following:
>
> void main()
> {
>	std::map<int, boost::shared_ptr<vehicle> > myMap;
>	factory::make(myMap);
> }
>
> After this the map should contain one object from type car with the
key
> 1, and one object from type bicycle with the key 2.
I tried now the following:
namespace factory
{

template <typename T = boost::mpl::_1>
struct tag{};

template <typename C>
struct mv{
    template <typename T>
                void operator()(tag<T>)
        {
                m_c.insert(std::make_pair(T::_key, typename
C::value_type(new T)));
        }
    mv(C& v):m_c(v){}
private:
    C& m_c;
};

template <typename T>
mv<T> make_mv(T& t){return mv<T>(t);}
}

int _tmain(int argc, _TCHAR* argv[])
{
    using namespace boost;
    using namespace boost::mpl;
    std::map<int, shared_ptr<vehicle> > vs;
    for_each<vector<car,train>,factory::tag<> >(factory::make_mv(vs));
    return 0;
}

With that I got the following compiler-error:
error C2440: 'Typeconversion': 'boost::mpl::bind1<F,T1>::apply<U1>::t1
*' can't be converted in 'std::_Tree<_Traits>::value_type'
        with
        [
            F=boost::mpl::quote1<factory::tag>,
            T1=boost::mpl::lambda_impl<boost::mpl::_1>::type,
            U1=item
        ]
        and
        [
 
_Traits=std::_Tmap_traits<int,boost::shared_ptr<vehicle>,std::less<int>,
std::allocator<std::pair<const int,boost::shared_ptr<vehicle>>>,false>
        ]

How can I elminiate this error?

Can somebody tell me when the book about the mpl will be available?

Thanks in advance
Sebastian