Question

I wrote this little code

std::map<int,template<class T>> map_;
map_.insert(make_pair<int,message>(myMsg.id,myMsg));

but the compiler doesn’t seem to get it and displays as an error

template argument 2 is invalid

and when I tried to correct by doing this

template<class T>
std::map<int,T> map_;

it displays as an error :

expected primary-expression before ‘template’ |

error: expected ‘;’ before ‘template’

Answer 1

I’m not sure about this, but you are trying to declare a variable, and that definition has to be fully defined. Trying to use a template doesn’t fully define the variable.

You can wrap it in a structure if you want to:

template<typename T>
struct Wrapper
{
    typedef std::map<int, T> map_type;
};

Then use it like this:

Wrapper<std::string>::map_type my_wrapped_map;
my_wrapped_map[1] = "Foo";