CompareBookmarks メソッドの例 (VC++)
この例では、CompareBookmarks メソッドのデモを行います。 特定のブックマークが特殊なものでない限り、ブックマークの相対値が必要になることはほとんどありません。
Authors テーブルから派生した Recordset のランダムな行を、検索のターゲットとして指定します。 次に、そのターゲットを基準とした各行の相対位置を表示します。
// BeginCompareBookmarksCpp.cpp
// compile with: /EHsc
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")
#include <ole2.h>
#include <stdio.h>
#include <conio.h>
#include <time.h>
#include <stdlib.h>
// Function declarations
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };
void CompareBookMarksX();
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
int main() {
if ( FAILED(::CoInitialize(NULL)) )
return -1;
CompareBookMarksX();
::CoUninitialize();
}
void CompareBookMarksX() {
HRESULT hr = S_OK;
_bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");
// Initialize pointers on define. These are in the ADODB:: namespace.
_RecordsetPtr pRstAuthors = NULL;
_variant_t vTarget;
_bstr_t strAns;
_bstr_t strTitle;
strTitle = "CompareBookmarks Example";
try {
TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));
pRstAuthors->Open("SELECT * FROM authors ORDER BY au_id", strCnn, adOpenStatic, adLockReadOnly, adCmdText);
long count = pRstAuthors->RecordCount;
printf("Rows in the Recordset = %d\n", count);
if (count == 0)
exit(1); // Exit if an empty recordset
srand( (unsigned)time( NULL ) ); // Randomize
count = int(rand() % (count-1)); // Get position between 1 and count-1
if (!count)
count++;
printf("Randomly chosen row position = %d\n", count);
_variant_t vtBookMark = (short)adBookmarkFirst;
pRstAuthors->Move(count,vtBookMark); // Move row to random position
vTarget = pRstAuthors->Bookmark; // Remember the mystery row.
count = 0;
pRstAuthors->MoveFirst();
while (!(pRstAuthors->EndOfFile)) { // Loop through recordset
long result = pRstAuthors->CompareBookmarks(pRstAuthors->Bookmark, vTarget);
if (result == adCompareNotEqual)
printf("Row %d: Bookmarks are not equal. %d\n", count, result);
else if (result == adCompareNotComparable)
printf("Row %d: Bookmarks are not comparable.\n", count);
else {
switch(result) {
case adCompareLessThan:
strAns = "less than";
break;
case adCompareEqual:
strAns = "equal to";
break;
case adCompareGreaterThan:
strAns = "greater than";
break;
default:
strAns = "in error comparing to";
break;
}
printf ("Row position %d is %s the target.\n",
count,(LPCSTR)strAns);
}
count++;
pRstAuthors->MoveNext();
}
}
catch(_com_error &e) {
// Notify the user of errors if any.
// Pass a connection pointer accessed from the Recordset.
_variant_t vtConnect = pRstAuthors->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 (pRstAuthors)
if (pRstAuthors->State == adStateOpen)
pRstAuthors->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, 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);
}