ADO中_variant_t变量的使用与转换

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用ADO做数据库，有个麻烦的事情就是_variant_t变量的使用，使用本例中封装的CConvert类转换就方便了。

 

 

// Convert.h: interface for the CConvert class.////////////////////////////////////////////////////////////////////////#if !defined(AFX_CONVERT_H__EC38F865_4607_4659_BAC8_AA6096C50EC7__INCLUDED_)#define AFX_CONVERT_H__EC38F865_4607_4659_BAC8_AA6096C50EC7__INCLUDED_#if _MSC_VER > 1000#pragma once#endif // _MSC_VER > 1000//////////////////////////////////////////////////////////////////////// Construction/Destruction/* * Copyright (c) 2010,[e-mail]* All rights reserved. * * 文件名称：Convert.h * 文件标识：数据类型转换* 摘 要：主要简化ADO中数据类型的转换 * * 当前版本：1.0 * 作 者：[e-mail]（注意把中文字符换成英文字符）* 完成日期：2010年5月11日 * 发布Blog：http://blog.csdn.net/zyq5945/ * */ //////////////////////////////////////////////////////////////////////#define TS(value) CConvert::ToString(value)class CConvert {public:static CString ToString(BYTE btValue);static CString ToString(int iValue);static CString ToString(unsigned int iValue);static CString ToString(long lValue);static CString ToString(unsigned long lValue);static CString ToString(__int64 i64Value);static CString ToString(unsigned __int64 i64Value);static CString ToString(float fltValue);static CString ToString(double dblValue);static CString ToString(const COleDateTime& time);static CString ToString(const _variant_t& var);public:static BYTE ToByte(LPCTSTR lpszValue);static int ToInt(LPCTSTR lpszValue);static unsigned int ToUInt(LPCTSTR lpszValue);static long ToLong(LPCTSTR lpszValue);static unsigned long ToULong(LPCTSTR lpszValue);static __int64 ToInt64(LPCTSTR lpszValue);static unsigned __int64 ToUInt64(LPCTSTR lpszValue);static float ToFloat(LPCTSTR lpszValue);static double ToDouble(LPCTSTR lpszValue);static COleDateTime ToTime(LPCTSTR lpszValue);static _variant_t ToVariant(const COleDateTime& time);};extern CConvert Convert;#endif // !defined(AFX_CONVERT_H__EC38F865_4607_4659_BAC8_AA6096C50EC7__INCLUDED_)

 

// Convert.cpp: implementation of the CConvert class.////////////////////////////////////////////////////////////////////////#include "stdafx.h"#include "Convert.h"#include <comutil.h>#include <comdef.h>#ifdef _DEBUG#undef THIS_FILEstatic char THIS_FILE[]=__FILE__;#define new DEBUG_NEW#endif//////////////////////////////////////////////////////////////////////// Construction/Destruction/* * Copyright (c) 2010,[e-mail]* All rights reserved. * * 文件名称：Convert.cpp * 文件标识：数据类型转换* 摘 要：主要简化ADO中数据类型的转换 * * 当前版本：1.0 * 作 者：[e-mail]（注意把中文字符换成英文字符）* 完成日期：2010年5月11日 * 发布Blog：http://blog.csdn.net/zyq5945/* */ //////////////////////////////////////////////////////////////////////CConvert Convert;CString CConvert::ToString(BYTE btValue){CString strValue;strValue.Format(_T("%d"), btValue);return strValue;}CString CConvert::ToString(int iValue){CString strValue;strValue.Format(_T("%d"), iValue);return strValue;}CString CConvert::ToString(unsigned int iValue){CString strValue;strValue.Format(_T("%u"), iValue);return strValue;}CString CConvert::ToString(long lValue){CString strValue;strValue.Format(_T("%d"), lValue);return strValue;}CString CConvert::ToString(unsigned long lValue){CString strValue;strValue.Format(_T("%u"), lValue);return strValue;}CString CConvert::ToString(__int64 i64Value){CString strValue;strValue.Format(_T("%I64d"), i64Value);return strValue;}CString CConvert::ToString(unsigned __int64 i64Value){CString strValue;strValue.Format(_T("%I64u"), i64Value);return strValue;}CString CConvert::ToString(float fltValue){CString strValue;strValue.Format(_T("%f"), fltValue);return strValue;}CString CConvert::ToString(double dblValue){CString strValue;strValue.Format(_T("%f"), dblValue);return strValue;}// 时间输出格式：2010-05-06 22:07:08CString CConvert::ToString(const COleDateTime& time){CString strValue;strValue = time.Format(_T("%Y-%m-%d %H:%M:%S"));return strValue;}CString CConvert::ToString(const _variant_t& var){CString strValue;switch (var.vt){case VT_BSTR: //字符串case VT_LPSTR:case VT_LPWSTR:strValue = (LPCTSTR)(_bstr_t)var;break;case VT_I1: //无符号字符case VT_UI1:strValue.Format(_T("%d"), var.bVal);break;case VT_I2: //短整型strValue.Format(_T("%d"), var.iVal);break;case VT_UI2: //无符号短整型strValue.Format(_T("%u"), var.uiVal);break;case VT_INT: //整型strValue.Format(_T("%d"), var.intVal);break;case VT_I4: //整型case VT_I8: //长整型strValue.Format(_T("%d"), var.lVal);break;case VT_UINT: //无符号整型strValue.Format(_T("%d"), var.uintVal);break;case VT_UI4: //无符号整型case VT_UI8: //无符号长整型strValue.Format(_T("%d"), var.ulVal);break;case VT_VOID:strValue.Format(_T("%08x"), var.byref);break;case VT_R4: //浮点型strValue.Format(_T("%f"), var.fltVal);break;case VT_R8: //双精度型strValue.Format(_T("%f"), var.dblVal);break;case VT_DECIMAL: //小数strValue.Format(_T("%f"), (double)var);break;case VT_CY:{COleCurrency cy = var.cyVal;strValue = cy.Format();}break;case VT_BLOB:case VT_BLOB_OBJECT:case 0x2011:strValue = _T("[BLOB]");break;case VT_BOOL: //布尔型 strValue = var.boolVal ? _T("TRUE") : _T("FALSE");break;case VT_DATE: //日期型{DATE dt = var.date;COleDateTime da = COleDateTime(dt);strValue = da.Format(_T("%Y-%m-%d %H:%M:%S"));}break;case VT_NULL://NULL值case VT_EMPTY: //空strValue = _T("");break;case VT_UNKNOWN: //未知类型default:strValue = _T("VT_UNKNOW");break;}return strValue;}BYTE CConvert::ToByte(LPCTSTR lpszValue){BYTE btValue;btValue = (BYTE)_ttoi(lpszValue);return btValue;}int CConvert::ToInt(LPCTSTR lpszValue){int iValue;iValue = _ttoi(lpszValue);return iValue;}unsigned int CConvert::ToUInt(LPCTSTR lpszValue){unsigned int iValue;iValue = _ttoi(lpszValue);return iValue;}long CConvert::ToLong(LPCTSTR lpszValue){long lValue;lValue = _ttol(lpszValue);return lValue;}unsigned long CConvert::ToULong(LPCTSTR lpszValue){unsigned long lValue;lValue = _ttol(lpszValue);return lValue;}__int64 CConvert::ToInt64(LPCTSTR lpszValue){__int64 i64Value;i64Value = _ttoi64(lpszValue);return i64Value;}unsigned __int64 CConvert::ToUInt64(LPCTSTR lpszValue){unsigned __int64 i64Value;i64Value = _ttoi64(lpszValue);return i64Value;}float CConvert::ToFloat(LPCTSTR lpszValue){float fltValue;#ifdef _MBCSfltValue = (float)atof(lpszValue);#elsefltValue = (float)wtof(lpszValue);#endifreturn fltValue;}double CConvert::ToDouble(LPCTSTR lpszValue){double dblValue;#ifdef _MBCSdblValue = atof(lpszValue);#elsedblValue = wtof(lpszValue);#endifreturn dblValue;}// 时间格式例子：2010-05-06 22:07:08// 2010 05 06 22 07 08// 2010:05:06 22:07:08// 2010-05-06-22-07-08// 只要是“- :”分割的时间格式都符合COleDateTime CConvert::ToTime(LPCTSTR lpszValue){unsigned int iArray[6] = {2010, 5, 11, 12, 00, 00};int nIndex = 0;#if _MSC_VER >= 1310 //VC6.0不支持CStringAlt::TokenizeCString strTmp;int curPos = 0;CString strValue(lpszValue);strTmp = strValue.Tokenize(_T("- :"),curPos);while (strTmp != _T("") && nIndex <6){iArray[nIndex++] = ToUInt(strTmp);strTmp = strValue.Tokenize(_T("- :"), curPos);};#elseTCHAR tChar[MAX_PATH] = {0};TCHAR tCharTmp[MAX_PATH] = {0};TCHAR seps[] = "- :";TCHAR *next_token = NULL;ASSERT(_tcslen(lpszValue) < MAX_PATH);RtlCopyMemory(tChar, lpszValue, _tcslen(lpszValue) * sizeof(TCHAR));next_token = _tcstok(tChar, seps);while ( next_token != NULL && nIndex <6){iArray[nIndex++] = _ttoi(next_token);next_token = _tcstok( NULL, seps);}#endifCOleDateTime time(iArray[0], iArray[1], iArray[2],iArray[3], iArray[4], iArray[5]);return time;}_variant_t CConvert::ToVariant(const COleDateTime& time){_variant_t vtVal;vtVal.vt = VT_DATE;vtVal.date = time;return vtVal;}

 

 

由于_variant_t重载了以下等号运算符，所以下面类型可以直接给_variant_t赋值

VARIANT VARIANT* _variant_tshort longfloatdoubleCY_bstr_twchar_tcharIDispatch*boolIUnknown*DECIMALBYTEcharunsigned shortunsigned longintunsigned int__int64unsigned __int64

 

由于COleDateTime重载了以下等号运算符，所以下面类型可以直接给COleDateTime赋值

VARIANTDATEtime_t__time64_tSYSTEMTIMEFILETIMEUDATE

 

本例中CConvert类也增加了一个ToVariant函数把COleDateTime转换为_variant_t类型变量

_variant_t varValue;CString strValue;COleDateTime dt;try{// 写入各字段值m_pRecordset->AddNew();// byte变量GetDlgItemText(IDC_EDIT1, strValue);varValue = CConvert::ToByte(strValue);m_pRecordset->PutCollect("tByte", varValue);// int变量GetDlgItemText(IDC_EDIT2, strValue);varValue = (long)CConvert::ToInt(strValue);m_pRecordset->PutCollect("tInt", varValue);// long变量GetDlgItemText(IDC_EDIT3, strValue);varValue = CConvert::ToLong(strValue);m_pRecordset->PutCollect("tLong", varValue);// float变量GetDlgItemText(IDC_EDIT4, strValue);varValue = CConvert::ToFloat(strValue);m_pRecordset->PutCollect("tFloat", varValue);// double变量GetDlgItemText(IDC_EDIT5, strValue);varValue = CConvert::ToDouble(strValue);m_pRecordset->PutCollect("tDouble", varValue);// COleDateTime变量GetDlgItemText(IDC_EDIT6, strValue);dt = CConvert::ToTime(strValue);varValue = CConvert::ToVariant(dt);m_pRecordset->PutCollect("tTime", varValue);// bool变量GetDlgItemText(IDC_EDIT7, strValue);if (!strValue.CompareNoCase("TRUE")){varValue = true;}else{varValue = false;}m_pRecordset->PutCollect("tBool", varValue);// 字符串变量GetDlgItemText(IDC_EDIT8, strValue);varValue = strValue;m_pRecordset->PutCollect("tText", varValue);m_pRecordset->Update();// 更新显示其库内容int nCurSel = m_list.GetItemCount();ADOListRecord();SetListSel(nCurSel);AfxMessageBox("插入成功!");}catch(_com_error& e){dump_com_error(e);}

参考文献：ADO数据库编程-总结2