How to retrieve a boost::variant value for a templated class

I am trying to use the boost::variant in c++11 to create this but I m not sure how. So I have this structure of the templated class data<>

typedef boost::variant< data<A>,data<B>> dataVar;

stored in a

std::map<string,dataVar> dataMap

It would be great if I could retrieve the type for data somehow so I can assign the values but I have no idea how to make this work elegantly

void registerDataFor(string str)
  {
     auto itr = dataMap.find(str);

    if(itr == dataMap.end())
        return;

     dataVar = itr->second;
     data<v.which()> itemData= boost::get<v.which()>(v);
     someArray.push_back(itemData.getIntegerValue());
     registerDataFor(itemData.getString());
  }

This doesn't compile since the template brackets require a static type.

I ve seen other responses proposing a visitor design but I also need the type for data<> to get the item.