Quick Q:Is it possible in C++ to iterate over a std::map with unpacked key and value?
Quick A: An easy solution is not supported by the standard, it may come later.
Recently on SO:
Is it possible in C++ to do std::map<> “for element : container” iteration with named variables (eg, key and value) instead of .first and .second?
You could write a class template:
template <class K, class T> struct MapElem { K const& key; T& value; MapElem(std::pair<K const, T>& pair) : key(pair.first) , value(pair.second) { } };with the advantage of being able to write
keyandvaluebut with the disadvantage of having to specify the types:for ( MapElem<int, std::string> kv : my_map ){ std::cout << kv.key << " --> " << kv.value; }And that won't work if
my_mapwereconsteither. You'd have to do something like:template <class K, class T> struct MapElem { K const& key; T& value; MapElem(std::pair<K const, T>& pair) : key(pair.first) , value(pair.second) { } MapElem(const std::pair<K const, std::remove_const_t<T>>& pair) : key(pair.first) , value(pair.second) { } }; for ( MapElem<int, const std::string> kv : my_map ){ std::cout << kv.key << " --> " << kv.value; }It's a mess. Best thing for now is to just get used to writing
.firstand.secondand hope that the structured bindings proposal passes, which would allow for what you really want:for (auto&& [key, value] : my_map) { std::cout << key << " --> " << value; }
