www.xdb2.com/Example/Ex006.asp demos how to link a user-defined C
function (DisplayInfo_r) to a class (person) and then have instances
(john, mary) invoke the inherited function.

void FunctionLinkAndInherit_Demo()
{
// Create person in db.
int* pPerson = T_create();
T_Name_relate(&pPerson, _T("person"));
T_relate(&pPerson, &pReCls_g, &pThing_g);

// Link a C function (DisplayInfo_r listed below) to person in db.
T_Fn_relate(&pPerson, DisplayInfo_r, _T("displayInfo"));

// Create age in db.
int* pAge = T_create();
T_Name_relate(&pAge, _T("age"));
T_relate(&pAge, &pReCls_g, &pThing_g);

// Create color in db.
int* pColor = T_create();
T_Name_relate(&pColor, _T("color"));
T_relate(&pColor, &pReCls_g, &pThing_g);

// Create john, an instance of person.
// Set his age to 35.
int* pJohn = T_create();
T_Name_relate(&pJohn, _T("john"));
T_relate(&pJohn, &pReCls_g, &pPerson);
T_Val_relate(&pJohn, &pAge, _T("35"));

// Create mary, an instance of person.
// Set her age to 25, and color to brown.
int* pMary = T_create();
T_Name_relate(&pMary, _T("mary"));
T_relate(&pMary, &pReCls_g, &pPerson);
T_Val_relate(&pMary, &pAge, _T("25"));
T_Val_relate(&pMary, &pColor, _T("brown"));

// Get thing for function displayInfo.
int* pFnDispInfo = Str_getDefT(_T("displayInfo"));

// Have john execute function displayInfo
// which he inherits from his class (person).
// Following displays "john cls person. john is 35." in a dialog
box.
T_Fn_execute_r(pJohn, pFnDispInfo);

// Have mary execute function displayInfo
// which she inherits from her class (person).
// Following displays "mary cls person. mary is 25. mary is
brown."
T_Fn_execute_r(pMary, pFnDispInfo);
}

/************************************************** ******************
Displays pT's values. (ie 'john is 35. john is brown.')
If pT has no values, displays pT's name. (ie 'john')
************************************************** ******************/
ERR_CODE DisplayInfo_r(int* pT)
{
TCHAR sT[kStrSz_g+1] = _T("");
T_Name_get(pT, sT, kStrSz_g);

BOOL hasProperty_b = FALSE;
TCHAR sInfo[kStrSz_g+1] = _T("");
int* pA[] = {NULL, pT, pS_g, NULL};
int* pB[] = {NULL, (int*)pA, pN_g, NULL};
while (int* pN=X2(pB)){
if (pReName_g != N_getV(pN)){
hasProperty_b = TRUE;

TCHAR sProp[kStrSz_g+1] = _T("");
T_Name_get(N_getV(pN), sProp, kStrSz_g);

TCHAR sVal[kStrSz_g+1] = _T("");
T_Name_get(N_getO(pN), sVal, kStrSz_g);

TCHAR sSent[kStrSz_g+1] = _T("");
_stprintf(sSent, _T("%s %s %s.\n"), sT, sProp, sVal);

_tcscat(sInfo, sSent);
}
}

if (hasProperty_b){
MessageBox(NULL, sInfo, kAppName_sg, MB_OK);
}
else{
MessageBox(NULL, sT, kAppName_sg, MB_OK);
}

return kErrNone_g;
}


To have john execute the inherited function via the GUI:
1. Select thing/person/john.
2. Ctrl+E (execute).
3. Select thing/function/displayInfo or thing/person/displayInfo.
4. Ctrl+V (paste).