template specialization for constructor of a parent class - c++

Question

I got a BaseType which is templated and want to inheritance it with an ArrayItem class. Since i want to use them as stencil for memory i want the ArrayItem class to know which type we have. So i'd like to specialize the constructor for some of the Template values for example long long.
template<typename T>
class ArrayItem : public BaseType<T>
{
public:
inline ArrayItem(T& t);
inline ETypes getType();
private:
ETypes m_type;
};
And the hpp should look like this:
template <typename T>
ArrayItem<T>::ArrayItem (T& t): BaseType(t)
{
}
template <>
ArrayItem<long long>::ArrayItem(long long& t) : BaseType<long long>(t) // this
{
m_type = INT;
}
template<typename T>
inline ETypes ArrayItem<T>::getType()
{
return m_type;
}
But the how do i do this specialization here?
enum ETypes
{
INT,
BOOL,
OBJECT,
ARRAY,
DOUBLE,
STRING
};
template <typename T>
class BaseType
{
public:
BaseType();
explicit BaseType(T& t);
protected:
union DataUnion
{
T data;
size_t size; //to make it at least 64bit
explicit DataUnion(T& t);
} m_data;
};
template <typename T>
BaseType<T>::DataUnion::DataUnion(T& t)
{
this->data = t;
}
template <typename T>
BaseType<T>::BaseType(T& t) : m_data(t) {}
template<typename T>
class ArrayItem : public BaseType<T>
{
public:
explicit inline ArrayItem(T& t);
inline ETypes getType();
private:
ETypes m_type;
};
template <typename T>
ArrayItem<T>::ArrayItem (T& t): BaseType<T>(t)
{
}
template <>
ArrayItem<long long>::ArrayItem(long long& t) : BaseType<long long>(t) // this
{
m_type = INT;
}
template<typename T>
inline ETypes ArrayItem<T>::getType()
{
return m_type;
}
int main()
{
long long somenumber = 1234;
ArrayItem<long long> item(somenumber);
if(item.getType() == INT)
std::cout<< "inttype";
//after this we can stancil the ptr to a
//BaseType<long long> since we know it's a long here
}

Answer 1

What you have looks right to me, outside of not providing the template arguments to BaseType for the typical case.
Here's a simple demo:
#include <iostream>
template <typename T>
struct B { };
template <typename T>
struct D : B<T> {
D(T );
};
template <typename T>
D<T>::D(T )
: B<T>()
{
std::cout << "def\n";
}
template <>
D<long>::D(long )
: B<long>()
{
std::cout << "hi\n";
}
int main()
{
D<int> i(4); // prints def
D<long> l(5); // prints hi
}