Move Method Example (VC++)

Move Method Example (VC++)

This example uses the Move method to position the record pointer based on user input.

#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
    no_namespace rename("EOF", "EndOfFile")

#include <stdio.h>
#include <ole2.h>
#include <stdlib.h>
#include <conio.h>
#include "MoveX.h"

// Function Declaration.
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void MoveX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

///////////////////////////////////////////////////////////
//                                                       //
//      Main Function                                    //
//                                                       //
///////////////////////////////////////////////////////////
void main()
{
    if(FAILED(::CoInitialize(NULL)))
        return;

    MoveX();

    ::CoUninitialize();
}

//////////////////////////////////////////////////
//                                              //
//      MoveX Function                          //
//                                              //
//////////////////////////////////////////////////

void MoveX(void)
{
    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _RecordsetPtr  pRstAuthors    = NULL;

    // Define Other Variables
    IADORecordBinding   *picRs = NULL;  //Interface Pointer declared  
    CAuthorsRs    authorsrs;         //C++ class object
    HRESULT hr = S_OK;

    // Open Authors table
    _bstr_t strCnn("Provider=sqloledb;Data Source=SRV;"
            "Initial Catalog=Pubs;User Id=sa;Password=;");

    try
    {
        // Open recordset from Authors table.
        TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));

        pRstAuthors->CursorType = adOpenStatic;
        // Use client cursor to allow use of AbsolutePosition property.
        pRstAuthors->CursorLocation = adUseClient;

        pRstAuthors->Open("SELECT au_id, au_fname, au_lname, city, "
            "state FROM Authors ORDER BY au_lname", strCnn, adOpenStatic, 
            adLockReadOnly, adCmdText);

        // Open an IADORecordBinding interface pointer which we'll use 
        // for Binding Recordset to a class.
        TESTHR(pRstAuthors->QueryInterface(
            __uuidof(IADORecordBinding),(LPVOID*)&picRs));

        // Bind the Recordset to a C++ Class here.
        TESTHR(picRs->BindToRecordset(&authorsrs));

        pRstAuthors->MoveFirst();

        while(true)
        {
            // Display information about current record and ask how many 
            // records to move.
            printf("Record %ld of %d\n", pRstAuthors->AbsolutePosition, 
                pRstAuthors->RecordCount);
            printf("Author: %s %s\n", 
                authorsrs.lemp_fnameStatus == adFldOK ? 
                authorsrs.m_au_fname : "<NULL>", 
                authorsrs.lemp_lnameStatus == adFldOK ? 
                authorsrs.m_au_lname : "<NULL>");
            printf("Location: %s, %s\n\n", 
                authorsrs.lemp_cityStatus == adFldOK ? 
                authorsrs.m_au_city : "<NULL>", 
                authorsrs.lemp_stateStatus == adFldOK ? 
                authorsrs.m_au_state : "<NULL>");

            char *strMove;
            char strTemp[5];
            printf("Enter number of records to Move "
                "\n(positive or negative, Enter to quit): ");
            gets(strTemp);

            strMove = strtok(strTemp," ");

            if (strMove == NULL)
                break;

            // if the input is not numeric then notify the user.
            if(!atol(strMove))
            {
                printf("Expecting numeric value...\n");
                continue;
            }

            // Store bookmark in case the Move goes too far 
            // forward or backward.
            _variant_t varBookmark = pRstAuthors->Bookmark;

            // Move method requires parameter of data type Long.
            long lngMove = atol(strMove);

            pRstAuthors->Move(lngMove);

            // Trap for BOF or EOF.
            if(pRstAuthors->BOF)
            {
                printf("Too far backward! Returning to current"
                    " record.\n");
                pRstAuthors->Bookmark = varBookmark;
            }

            if(pRstAuthors->EndOfFile)
            {
                printf("Too far forward! Returning to current"
                    " record.\n");
                pRstAuthors->Bookmark = varBookmark;
            }
        }
        // Clean up objects before exit.
        pRstAuthors->Close();
        // Release the IADORecordset Interface here.
        if (picRs)
            picRs->Release();
    }

    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 occured.");
                break;
        }
    }
}

///////////////////////////////////////////////////////////
//                                                       //
//      PrintProviderError Function                      //
//                                                       //
///////////////////////////////////////////////////////////

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("\t Error number: %x\t%s", pErr->Number,
                 (LPCSTR) pErr->Description);
        }
    }
}

///////////////////////////////////////////////////////////
//                                                       //
//      PrintComError Function                           //
//                                                       //
///////////////////////////////////////////////////////////

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);
}

MoveX.h:

// MoveX.h

#include "icrsint.h"


// This Class extracts fname, lname, city and state
// from the "Authors" table.

class CAuthorsRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CAuthorsRs)

    // Column au_id is the 1st field in the recordset   

    ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_au_fname, 
         sizeof(m_au_fname), lemp_fnameStatus, TRUE)

    ADO_VARIABLE_LENGTH_ENTRY2(3, adVarChar, m_au_lname, 
         sizeof(m_au_lname), lemp_lnameStatus, TRUE)

    ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_au_city, 
         sizeof(m_au_city), lemp_cityStatus, TRUE)

    ADO_VARIABLE_LENGTH_ENTRY2(5, adChar, m_au_state, 
         sizeof(m_au_state), lemp_stateStatus, TRUE)

END_ADO_BINDING()

public:
    char     m_au_fname[21];
    ULONG    lemp_fnameStatus;
    char     m_au_lname[41];
    ULONG    lemp_lnameStatus;
    char     m_au_city[21];
    ULONG    lemp_cityStatus;
    char     m_au_state[3];
    ULONG    lemp_stateStatus;
};