Ejemplo del método Supports (VC ++)

En este ejemplo se usa el método Supports para mostrar las opciones que admite un conjunto de registros abierto con distintos tipos de cursor. La función DisplaySupport es necesaria para que se ejecute este ejemplo.

// SupportsMethodExample.cpp  
// compile with: /EHsc  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <stdio.h>  
#include <ole2.h>  
#include <conio.h>  
  
// Function Declarations.  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
  
void SupportsX();  
void DisplaySupport(_RecordsetPtr pRstTemp);  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1;  
   SupportsX();  
   ::CoUninitialize();  
}  
  
void SupportsX() {  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _RecordsetPtr pRstTitles = NULL;  
  
   // Assign connection string to a variable  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   try {  
      // Open a recordset from Titles table  
      TESTHR(pRstTitles.CreateInstance(__uuidof(Recordset)));  
  
      // Fill array with CursorType constants.  
      int aintCursorType[4];  
      aintCursorType[0] = adOpenForwardOnly;  
      aintCursorType[1] = adOpenKeyset;  
      aintCursorType[2] = adOpenDynamic;  
      aintCursorType[3] = adOpenStatic;  
  
      // Open recordset using each CursorType and optimistic locking.  
      // Then call the DisplaySupport procedure to display the supported options.  
      for (int intIndex=0 ; intIndex <= 3 ; intIndex++) {  
         pRstTitles->CursorType = (enum CursorTypeEnum)aintCursorType[intIndex];  
         pRstTitles->LockType = adLockOptimistic;  
  
         // Pass the Cursor type and LockType to the Recordset.  
         pRstTitles->Open ("titles", strCnn,   
            (enum CursorTypeEnum)aintCursorType[intIndex], adLockOptimistic, adCmdTable);  
  
         switch(aintCursorType[intIndex]) {  
         case adOpenForwardOnly:  
            printf("\nForwardOnly cursor supports:\n");  
            break;  
  
         case adOpenKeyset:  
            printf("\nKeyset cursor supports:\n");  
            break;  
  
         case adOpenDynamic:  
            printf("\nDynamic cursor supports:\n");  
            break;  
  
         case adOpenStatic:  
            printf("\nStatic cursor supports:\n");  
            break;  
  
         default :  
            break;  
         }  
  
         DisplaySupport(pRstTitles);  
      }  
   }  
   catch(_com_error &e) {  
      // Display errors, if any. Pass connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstTitles->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
      case VT_BSTR:  
         PrintComError(e);  
         break;  
      case VT_DISPATCH:  
         PrintProviderError(vtConnect);  
         break;  
      default:  
         printf("Errors occurred.");  
         break;  
      }  
   }  
  
   // Clean up objects before exit.  
   if (pRstTitles)  
      if (pRstTitles->State == adStateOpen)  
         pRstTitles->Close();  
}  
  
void DisplaySupport (_RecordsetPtr pRstTemp) {  
   // Fill array with cursor option constants.  
   long  alngConstants[11];  
   alngConstants[0] = adAddNew;  
   alngConstants[1] = adApproxPosition;  
   alngConstants[2] = adBookmark;  
   alngConstants[3] = adDelete;  
   alngConstants[4] = adFind;  
   alngConstants[5] = adHoldRecords;  
   alngConstants[6] = adMovePrevious;  
   alngConstants[7] = adNotify;  
   alngConstants[8] = adResync;  
   alngConstants[9] = adUpdate;  
   alngConstants[10] = adUpdateBatch;  
  
   for ( int intIndex = 0 ; intIndex <= 10 ; intIndex++ ) {  
      VARIANT_BOOL booSupports = pRstTemp->Supports( (enum CursorOptionEnum)alngConstants[intIndex] );  
  
      if (booSupports) {  
         switch(alngConstants[intIndex]) {  
         case adAddNew :  
            printf("\n  AddNew");  
            break;  
  
         case adApproxPosition :  
            printf("\n  AbsolutePosition and AbsolutePage");  
            break;  
  
         case adBookmark :  
            printf("\n  Bookmark");  
            break;  
  
         case adDelete :  
            printf("\n  Delete");  
            break;  
  
         case adFind :  
            printf("\n  Find");  
            break;  
  
         case adHoldRecords :  
            printf("\n  Holding Records");  
            break;  
  
         case adMovePrevious :  
            printf("\n  MovePrevious and Move");  
            break;  
  
         case adNotify :  
            printf("\n  Notifications");  
            break;  
  
         case adResync :  
            printf("\n  Resyncing data");  
            break;  
  
         case adUpdate :  
            printf("\n  Update");  
            break;  
  
         case adUpdateBatch :  
            printf("\n  Batch updating");  
            break;  
  
         default :  
            break;  
         }  
      }  
   }  
}  
  
void PrintProviderError(_ConnectionPtr pConnection) {  
   // Print Provider Errors from Connection object.  
   // pErr is a record object in the Connection's Error collection.  
   ErrorPtr pErr = NULL;  
  
   if ( (pConnection->Errors->Count) > 0 ) {  
      long nCount = pConnection->Errors->Count;  
      // Collection ranges from 0 to nCount -1.  
      for ( long i = 0 ; i < nCount ; i++ ) {  
         pErr = pConnection->Errors->GetItem(i);  
         printf("Error number: %x\t%s\n", pErr->Number, (LPCSTR) pErr->Description);  
      }  
   }  
}  
  
void PrintComError(_com_error &e) {  
   _bstr_t bstrSource(e.Source());  
   _bstr_t bstrDescription(e.Description());  
  
   // Print Com errors.  
   printf("Error\n");  
   printf("\tCode = %08lx\n", e.Error());  
   printf("\tCode meaning = %s\n", e.ErrorMessage());  
   printf("\tSource = %s\n", (LPCSTR) bstrSource);  
   printf("\tDescription = %s\n", (LPCSTR) bstrDescription);  
}  

Consulte también

Objeto de conjunto de registros (ADO)
Método Supports