Using Variant to Store Point

Using Variant to Store Point

 

Variant is a very powerful data type to store 'any' data. With the help of COM class _variant_t, VARIANT bacomes very easy to use. But _variant_t dosen't support all kinds of data type, for example, point data with two or three elements. Variant can hold pointer, but the memory management becomes a stubborn problem when copying variant. I'm trying to find a better way to solve the problem, but I don't want to rewrite a variant. So,  dose the way exist?

      Many UI-libs use variant to hold data of properties, such as BCGPControlBar, and they do support point displaying. Actually the point elements are formated to a string so that they be stored into one property. But it's very boring to parse values between points and variant, so it's a good idea to write a adapter for them. This adapter takes charge to format point data to string, extract point data from string, and ex-convert with _variant_t.

if we have a point class like this:

 

class  Point3D
{
public :
Point3D() {}
Point3D( double  x,  double  y,  double  z);
double  x();
double  y();
double  z();
private :
double  x, y, z;
} ;

 

we can write our point adapter as following:

 

class  PointAdapter
{
private :
CString m_strData;
public :
PointAdapter();
PointAdapter( const  Point3D &  point);
PointAdapter( const  _variant_t &  point);

operator  Point3D() const ;
operator  _variant_t() const ;
} ;

 

now, we can use the classes:

 

Point3D point( 1 , 2 , 3 );
_variant_t var  =  PointAdapter(point);
Point3D point2  =  PointAdapter(var);