I have this structure
static map<TypeA, pair<reference_wrapper<TypeB>, TypeC>> my_map;
Later, I access it like this:
pair<reference_wrapper<TypeB>, TypeC> instance = my_map[type_a_instance];
This error triggers:
no matching function for call to ‘std::pair<std::reference_wrapper< TypeB>, TypeC>::pair()’
>Solution :
map::operator[] must default construct the pair in the map if no mapping for the key exists. That’s not possible for the types in your map because of the reference_wrapper. Use find instead.
pair<reference_wrapper<TypeB>, TypeC> instance =
my_map.find(type_a_instance)->second;
Or use at as suggested by @Steve Lorimer
pair<reference_wrapper<TypeB>, TypeC> instance =
my_map.at(type_a_instance);
Of course both versions assume that the key can be found. The find version gives you undefined behaviour if the key is not found, the second gives a std::out_of_range exception.