A 2-dimensional array class

Array2D.cpp

#include <stdexcept>
// uses the Array<T> class
 
template <class T>
class Array2D
{
protected:
    unsigned int numberOfRows, numberOfColumns;
    Array<T> array;
public:
    class Row
    {
        Array2D& array2D;
        unsigned int const row;
    public:
        Row(Array2D& _array2D, unsigned int _row)
            : array2D(_array2D)
            , row(_row)
        { }
        
        T& operator[](unsigned int column) const
        { return array2D.Select(row, column); }
    };
    
    Array2D(unsigned int, unsigned in);
    T& Select(unsigned int, unsigned int);
    
    Row operator[](unsigned int);
};

template <class T>
Array2D<T>::Array2D(unsigned int n, unsigned int m)
    : numberOfRows(n)
    , numberOfColumns(m)
    , array(n * m)
{ }

template <class T>
T& Array2D<T>::Select(unsigned int i, unsigned int j)
{
    if (i >= numberOfRows)
        throw std::out_of_range("invalid row");
    if (i >= numberOfColumns)
        throw std::out_of_range("invalid column");
    return array[i * numberOfColumns + j];
}

template <class T>
typename Array2D<T>::Row Array2D<T>::operator[](unsigned int row)
{ return Row(*this, row); }

int main()
{
    Array2D<int> array(2, 2);
    array[0][0];
}