StayInSync プロパティの例 (VC++)
この例では、StayInSync プロパティを使用して、階層 Recordset 内の行へのアクセスを容易にする方法を示します。
外側のループで、各作成者の姓と名、状態、および ID が表示されます。 各行に追加された Recordset は Fields コレクションから取得され、親 Recordset が新しい行に移動するたびに StayInSync プロパティによって自動的に rstTitleAuthor に割り当てられます。 内部ループで、追加されたレコードセットの各行から 4 つのフィールドが表示されます。
// 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);
}