Cache for data to be shared between different instances

data_cache.hpp

#include <map>
#include <memory>

template <class Key, class Data>
class DataCache
{
public:
  template<typename... Args>
  std::shared_ptr<Data> GetData(const Key& key, Args... args)
  {
    auto it = map_.find(key);
    if (it != map_.end())
        if (auto data = it->second.lock())
            return data;

    auto data = std::make_shared<Data>(args...);
    map_[key] = data;
    return data;
  }
  
private:
  std::map<Key, std::weak_ptr<Data> > map_;
};