Filling a vector from a map of shared_pointers

Question

I have been trying to fill a vector from a map. I know how to do this in a more conventional way, but I was trying to achive it with STL algorithms (a one liner) as some kind of a training :).

the origin map type is :

std::map< std::string, boost::shared_ptr< Element > >

the destination vector is :

std::vector< Element > theVector;

what I have so far is this:

std::transform( theMap.begin(), theMap.end(),
        std::back_inserter( theVector ),
        boost::bind( &map_type::value_type::second_type::get, _1 )
        );

But this is trying to insert a pointer in the vector which doesn't work. I have also tried this:

using namespace boost::lambda;
using boost::lambda::_1;

std::transform( theMap.begin(), theMap.end(),
        std::back_inserter( theVector ),
        boost::bind( &map_type::value_type::second_type::get, *_1 )
        );

But it's not working either.

Edit:

I've got this working solution but I find it less impressive :)

std::for_each( theMap.begin(), theMap.end(), 
        [&](map_type::value_type& pair)
        {
            theVector.push_back( *pair.second );
        } );

Edit2: The thing I'm the less comfortable with here is bind(), so bind() solutions are welcome!

Answer 1

How about:

// Using std::shared_ptr and lambdas as the solution
// you posted used C++11 lambdas.
//
std::map<std::string, std::shared_ptr<Element>> m
    {
        { "hello", std::make_shared<Element>() },
        { "world", std::make_shared<Element>() }
    };
std::vector<Element> v;

std::transform(m.begin(),
               m.end(),
               std::back_inserter(v),
               [](decltype(*m.begin())& p) { return *p.second; });

See online demo at http://ideone.com/ao1C50 .

Answer 2

Another alternative may be the new for syntax:

for(auto &cur_pair: the_map) { theVector.push_back(*(cur_pair.second)); }

It's at least a one-liner (kinda), though it's just another way to do your std::for_each but more compact.