StayInSync, propriété - Exemple (VC++)

Cet exemple montre comment la propriété StayInSync facilite l’accès aux lignes d’un jeu d’enregistrements de hiérarchique.

La boucle externe affiche le prénom et le nom, l’état et l’identification de chaque auteur. Le Recordset ajouté pour chaque ligne est récupéré à partir de la collection Fields et automatiquement affecté à rstTitleAuthor par la propriété StayInSync chaque fois que le jeu d’enregistrements parent passe à une nouvelle ligne. La boucle interne affiche quatre champs de chaque ligne dans le jeu d’enregistrements ajouté.

// BeginStayInSyncCpp.cpp  
// compile with: /EHsc  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <ole2.h>  
#include <stdio.h>  
#include <conio.h>  
  
// Function declarations  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
void StayInSyncX();  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1 ;  
  
   StayInSyncX();  
   ::CoUninitialize();  
}  
  
void StayInSyncX() {  
   HRESULT  hr = S_OK;  
  
   // Define string variables.  
   _bstr_t strCnn("Provider='MSDataShape'; Data Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _ConnectionPtr pConnection = NULL;  
   _RecordsetPtr pRst = NULL;  
   _RecordsetPtr pRstTitleAuthor = NULL;  
  
   try {  
      TESTHR(pRstTitleAuthor.CreateInstance(__uuidof(Recordset)));  
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
      TESTHR(pRst.CreateInstance(__uuidof(Recordset)));  
  
      // Open connection.  
      pConnection->Open (strCnn, "", "", adConnectUnspecified);  
      pRst->PutStayInSync(true);  
  
      // Open recordset with names from Author & titleauthor table.  
      pRst->Open("SHAPE  {select * from authors} "   
         "APPEND ({select * from titleauthor}"  
         "RELATE au_id TO au_id) AS chapTitleAuthor",  
         _variant_t((IDispatch*)pConnection, true), adOpenStatic, adLockReadOnly, adCmdText);  
  
      pRstTitleAuthor = pRst->GetFields()->GetItem("chapTitleAuthor")->Value;  
      while (!(pRst->EndOfFile)) {      
         printf("\n%s  %s  %s    %s\n", (LPCSTR)(_bstr_t)pRst->  
            Fields->GetItem("au_fname")->Value,  
            (LPCSTR)(_bstr_t)pRst->Fields->GetItem("au_lname")->Value,  
            (LPCSTR)(_bstr_t)pRst->Fields->GetItem("state")->Value,   
            (LPCSTR)(_bstr_t)pRst->Fields->GetItem("au_id")->Value);  
  
         _variant_t vIndex;  
         while ( !(pRstTitleAuthor->EndOfFile) ) {  
            vIndex = (short) 0;  
            printf("%s    ",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
            vIndex = (short) 1;  
            printf("%s    ",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
            vIndex = (short) 2;  
            printf("%s    ",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
            vIndex = (short) 3;  
            printf("%s\n",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
  
            pRstTitleAuthor->MoveNext();  
         }  
         pRst->MoveNext();  
      }  
   }  
   catch(_com_error &e) {  
      // Notify user of errors, if any.  Pass connection pointer accessed from the Recordset.  
      PrintProviderError(pConnection);  
      PrintComError(e);     
   }  
  
   // Clean up objects before exit.  
   if (pRst)  
      if (pRst->State == adStateOpen)  
         pRst->Close();  
   if (pConnection)  
      if (pConnection->State == adStateOpen)  
         pConnection->Close();  
}  
  
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);  
}  

Voir aussi

Fields, collection (ADO)
objet Recordset (ADO)
StayInSync, propriété