自定义对象派生自acdb3dSolid一些问题？

Class Mysolid:AcDb3dSolid() // custom object inherits native acdb 3d solid
{
   private AcDb3dSolid * pNativeSolid; //pointer to native solid
   // this next function is private as we want to keep the native solid a secret ;)
   private AcDb3dSolid * GetNativeSolid ()
   {
       return this->pNativeSolid; // get the stored native solid
   }
   // a boolean subtraction operation for example:
   public void MySolidSubtractionOp (MySolid * pSolidCutter, MySolid * pSolidToBeCut)
   {
       //ok, we need to get both native solids:
       AcDb3dSolid * pSolCut = pSolidCutter->GetNativeSolid();
       AcDb3dSolid * pSoltobeCut = pSolidCutter->GetNativeSolid();
      // now we use the native operation using the native solids:
      // note this is only guessing here for an example!
      AcDb3dSolid * pResult = pSoltobeCut->booleanOperation(boolean::Subtract, pSolCut) // pass in operation type and cutting solid
      // now we have a result (if all went well, remember to check the result using errorstatus etc) we can wrap it back into the solid
      // since it was 'this' solid being cut, we store the pointer back in 'this' solid
      this->pNativeSolid = pResult;
   }
}