一、其它數據類型轉換為字符串
- 短整型(int)
itoa(i,temp,10);///將i轉換為字符串放入temp中,最后一個數字表示十進制
itoa(i,temp,2); ///按二進制方式轉換- 長整型(long)
ltoa(l,temp,10);- 浮點數(float,double)
用fcvt可以完成轉換,這是MSDN中的例子:
int decimal, sign;
char *buffer;
double source = 3.1415926535;
buffer = _fcvt( source, 7, &decimal, &sign );
運行結果:source: 3.1415926535 buffer: '31415927' decimal: 1 sign: 0
decimal表示小數點的位置,sign表示符號:0為正數,1為負數- CString變量
str = "2008北京奧運";
buf = (LPSTR)(LPCTSTR)str;- BSTR變量
BSTR bstrValue = ::SysAllocString(L"程序員");
char * buf = _com_util::ConvertBSTRToString(bstrValue);
SysFreeString(bstrValue);
AfxMessageBox(buf);
delete(buf);- CComBSTR變量
CComBSTR bstrVar("test");
char *buf = _com_util::ConvertBSTRToString(bstrVar.m_str);
AfxMessageBox(buf);
delete(buf);- _bstr_t變量
_bstr_t類型是對BSTR的封裝,因為已經重載了=操作符,所以很容易使用
_bstr_t bstrVar("test");
const char *buf = bstrVar;///不要修改buf中的內容
AfxMessageBox(buf);- 通用方法(針對非COM數據類型)
用sprintf完成轉換
char buffer[200]; char c = '1'; int i = 35; long j = 1000; float f = 1.7320534f; sprintf( buffer, "%c",c); sprintf( buffer, "%d",i); sprintf( buffer, "%d",j); sprintf( buffer, "%f",f);二、字符串轉換為其它數據類型
strcpy(temp,"123");- 短整型(int)
i = atoi(temp);- 長整型(long)l = atol(temp);
- 浮點(double) d = atof(temp);
- CString變量CString name = temp;
- BSTR變量BSTR bstrValue = ::SysAllocString(L"程序員");
...///完成對bstrValue的使用 SysFreeString(bstrValue);
- CComBSTR變量CComBSTR類型變量可以直接賦值 CComBSTR bstrVar1("test"); CComBSTR bstrVar2(temp);
- _bstr_t變量_bstr_t類型的變量可以直接賦值
_bstr_t bstrVar1("test");
_bstr_t bstrVar2(temp);
三、其它數據類型轉換到CString使用CString的成員函數Format來轉換,例如:
- 整數(int) str.Format("%d",i);
- 浮點數(float) str.Format("%f",i);
- 字符串指針(char *)等已經被CString構造函數支持的數據類型可以直接賦值 str = username;
- 對于Format所不支持的數據類型,可以通過上面所說的關于其它數據類型轉化到char *的方法先轉到char *,然后賦值給CString變量。
四、BSTR、_bstr_t與CComBSTR
- CComBSTR 是ATL對BSTR的封裝,_bstr_t是C++對BSTR的封裝,BSTR是32位指針,但并不直直指向字串的緩沖區。
char *轉換到BSTR可以這樣:
BSTR b=_com_util::ConvertStringToBSTR("數據");///使用前需要加上comutil.h和comsupp.lib
SysFreeString(bstrValue);
反之可以使用
char *p=_com_util::ConvertBSTRToString(b);
delete p;
具體可以參考一,二段落里的具體說明。
CComBSTR與_bstr_t對大量的操作符進行了重載,可以直接進行=,!=,==等操作,所以使用非常方便。
特別是_bstr_t,建議大家使用它。
五、VARIANT 、_variant_t 與 COleVariant
VARIANT的結構可以參考頭文件VC98\Include\OAIDL.H中關于結構體tagVARIANT的定義。
對于VARIANT變量的賦值:首先給vt成員賦值,指明數據類型,再對聯合結構中相同數據類型的變量賦值,舉個例子:
VARIANT va;
int a=2001;
va.vt=VT_I4;///指明整型數據
va.lVal=a; ///賦值
_variant_t是VARIANT的封裝類,其賦值可以使用強制類型轉換,其構造函數會自動處理這些數據類型。
使用時需加上#include <comdef.h>
例如:
long l=222;
ing i=100;
_variant_t lVal(l);
lVal = (long)i;
COleVariant的使用與_variant_t的方法基本一樣,請參考如下例子:
COleVariant v3 = "字符串", v4 = (long)1999;
CString str =(BSTR)v3.pbstrVal;
long i = v4.lVal;
////////////////////////////////////////////////////////////////////////////////////
本主題演示如何將各種 C++ 字符串類型轉換為其他字符串。以轉換的字符串類型包括 char *、wchar_t*、_bstr_t、CComBSTR、CString、basic_string 和 System.String。在所有情況下,在將字符串轉換為新類型時,都會創建字符串的副本。對新字符串進行的任何更改都不會影響原始字符串,反之亦然。
從 char * 轉換
// convert_from_char.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
char *orig = "Hello, World!";
cout << orig << " (char *)" << endl;
// Convert to a wchar_t*
size_t rigsize = strlen(orig) + 1;
const size_t newsize = 100;
size_t convertedChars = 0;
wchar_t wcstring[newsize];
mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a CString
CString cstring(orig);
cstring += " (CString)";
cout << cstring << endl;
// Convert to a basic_string
string basicstring(orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
輸出
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (basic_string)
Hello, World! (System::String)
從 wchar_t * 轉換
// convert_from_wchar_t.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
wchar_t *orig = L"Hello, World!";
wcout << orig << L" (wchar_t *)" << endl;
// Convert to a char*
size_t rigsize = wcslen(orig) + 1;
const size_t newsize = 100;
size_t convertedChars = 0;
char nstring[newsize];
wcstombs_s(&convertedChars, nstring, origsize, orig, _TRUNCATE);
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a CString
CString cstring(orig);
cstring += " (CString)";
cout << cstring << endl;
// Convert to a basic_string
wstring basicstring(orig);
basicstring += L" (basic_string)";
wcout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
輸出
Hello, World! (wchar_t *)
Hello, World! (char *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (basic_string)
Hello, World! (System::String)
-
從 _bstr_t 轉換
// convert_from_bstr_t.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
_bstr_t orig("Hello, World!");
wcout << orig << " (_bstr_t)" << endl;// Convert to a char*
const size_t newsize = 100;
char nstring[newsize];
strcpy_s(nstring, (char *)orig);
strcat_s(nstring, " (char *)");
cout << nstring << endl;// Convert to a wchar_t*
wchar_t wcstring[newsize];
wcscpy_s(wcstring, (wchar_t *)orig);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;// Convert to a CComBSTR
CComBSTR ccombstr((char *)orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}// Convert to a CString
CString cstring((char *)orig);
cstring += " (CString)";
cout << cstring << endl;// Convert to a basic_string
string basicstring((char *)orig);
basicstring += " (basic_string)";
cout << basicstring << endl;// Convert to a System::String
String ^systemstring = gcnew String((char *)orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
輸出Hello, World! (_bstr_t) Hello, World! (char *) Hello, World! (wchar_t *) Hello, World! (CComBSTR) Hello, World! (CString) Hello, World! (basic_string) Hello, World! (System::String)
從 CComBSTR 轉換
// convert_from_ccombstr.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"
using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;
int main()
{
CComBSTR orig("Hello, World!");
CW2A printstr(orig);
cout << printstr << " (CComBSTR)" << endl;
// Convert to a char*
const size_t newsize = 100;
char nstring[newsize];
CW2A tmpstr1(orig);
strcpy_s(nstring, tmpstr1);
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a wchar_t*
wchar_t wcstring[newsize];
wcscpy_s(wcstring, orig);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CString
CString cstring(orig);
cstring += " (CString)";
cout << cstring << endl;
// Convert to a basic_string
wstring basicstring(orig);
basicstring += L" (basic_string)";
wcout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
輸出
Hello, World! (CComBSTR) Hello, World! (char *) Hello, World! (wchar_t *) Hello, World! (_bstr_t) Hello, World! (CString) Hello, World! (basic_string) Hello, World! (System::String)
從 CString 轉換
// convert_from_cstring.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
CString orig("Hello, World!");
wcout << orig << " (CString)" << endl;
// Convert to a char*
const size_t newsize = 100;
char nstring[newsize];
strcpy_s(nstring, orig);
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a wchar_t*
// You must first convert to a char * for this to work.
size_t rigsize = strlen(orig) + 1;
size_t convertedChars = 0;
wchar_t wcstring[newsize];
mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a basic_string
string basicstring(orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
輸出
Hello, World! (CString)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (basic_string)
Hello, World! (System::String)
從basic_string 轉換
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
string orig("Hello, World!");
cout << orig << " (basic_string)" << endl;
// Convert to a char*
const size_t newsize = 100;
char nstring[newsize];
strcpy_s(nstring, orig.c_str());
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a wchar_t*
// You must first convert to a char * for this to work.
size_t rigsize = strlen(orig.c_str()) + 1;
size_t convertedChars = 0;
wchar_t wcstring[newsize];
mbstowcs_s(&convertedChars, wcstring, origsize, orig.c_str(), _TRUNCATE);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig.c_str());
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig.c_str());
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a CString
CString cstring(orig.c_str());
cstring += " (CString)";
cout << cstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig.c_str());
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}