std vector of pointer to template class

Question

I have a template class something like :

template <class TYPE>
class Temp {
public:
    Temp(TYPE _val) : var(_val){};
    TYPE var;
};

I want to store the objects on this template class in a STL container say vector.

void print(vector<Temp<TYPE> *> & _vec) {
    for(unsigned short i = 0; i < _vec.size() ; i++)
       cout << " Value of stored variable is : " << (*_vec[i]).var << endl;
}

int main(int argc, char* argv[]) {
    vector<Temp<TYPE> *> cont;
    Temp<int> t1(20);
    Temp<float> t2(1.4);
    cont.push_back(&t1);
    cont.push_back(&t2);
    return 0;        
}

I know that we cannot allocate a stl container without defining the type. Is there any way around to get this done ? and I cannot use boost.variant.

Answer 1

Your options include:

• Giving the distinct instantiations of Temp a common base class (with a virtual destructor), then storing pointers to the base type in the vector . You can then use dynamic_cast<> to check the run-time type of the stored objects, or you can add some type-indicating virtual function overridden in the derived instantiations.

• Writing your own discriminated union class, where an enum or int keeps track of the current type stored (if there's a fixed set).