container of template class in c++ - c++

Question

I have a template, which may be used with different stl map (map<int, int>, map<int, char>, etc.), as follows.
template <typename Map> struct TriMaps
{
Map& next;
Map& prev;
Map& curr;
};
so, TriMaps<init, int> intTriMaps; TriMaps<int, char> charTriMaps;
Then, is it possible to have a container of the above TriMaps, in different type? e.g.
vector <TriMaps> vecMaps;
which contain intTriMaps and charTriMaps? Usually container requires the same type. But I really need a container for my case. No boost or third library available.

Answer 1

First determine and finalize what this class template TriMaps is expected to do. In C++, you must initialize a reference to something. You probably need a non-reference type (or a pointer type). Consider:
template <typename Map>
struct TriMaps
{
Map next;
Map prev;
Map curr;
};
Usage:
TriMaps<int> IntMaps;
vector<TriMaps<int>> iv;
If you need two template type argument, you can do this way:
template <typename MapType1, typename MapType2>
struct TriMaps
{
MapType1 a;
Maptype2 b;
};
Usage:
TriMaps<int, float> IntMaps;
vector<TriMaps<int, float>> iv;
EDIT:
Carefully understand that following simple class will not compile.
class TriMap
{
int & ref_int;
};
One approach is to refer a global variable (just to make it compile), or take an int& via a constructor.
// Approach 1
int global;
class TriMap
{
int & ref_int;
public:
TriMap() : ref_int(global) {}
};
// Approach 2
class TriMap
{
int & ref_int;
public:
TriMap(int & outer) : ref_int(outer) {}
};

Answer 2

You can't have a std::vector of different type
but if you can have base class
struct TriMapBase { virtual ~TriMapBase() = default; };
template <typename Map> struct TriMaps : TriMapBase { /* Your implementation */ };
Then you may have:
TriMapBase<std::map<int, int>> mapint;
TriMapBase<std::map<int, char>> mapchar;
std::vector<TriMapBase*> v = {&mapint, &mapchar};
but you have to use virtual functions
or dynamic_cast to retrieve the correct type afterward...
or use