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其它數據類型轉換為字符串

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;
}

輸出
Hello, World! (basic_string)
Hello, World! (char )
Hello, World! (wchar_t )
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (System::String)

從 System::String 轉換

// convert_from_system_string.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()
{
    String ^orig = gcnew String("Hello, World!");
    Console::WriteLine("{0} (System::String)", orig);

    pin_ptr<const wchar_t> wch = PtrToStringChars(orig);

    // Convert to a char*
    size_t rigsize = wcslen(wch) + 1;
    const size_t newsize = 100;
    size_t convertedChars = 0;
    char nstring[newsize];
    wcstombs_s(&convertedChars, nstring, origsize, wch, _TRUNCATE);
    strcat_s(nstring, " (char )");
    cout << nstring << endl;

    // Convert to a wchar_t
    wchar_t wcstring[newsize];
    wcscpy_s(wcstring, wch);
    wcscat_s(wcstring, L" (wchar_t *)");
    wcout << wcstring << endl;

    // Convert to a _bstr_t
    _bstr_t bstrt(wch);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert to a CComBSTR
    CComBSTR ccombstr(wch);
    if (ccombstr.Append(L" (CComBSTR)") == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a CString
    CString cstring(wch);
    cstring += " (CString)";
    cout << cstring << endl;

    // Convert to a basic_string
    wstring basicstring(wch);
    basicstring += L" (basic_string)";
    wcout << basicstring << endl;

    delete orig;
}

posted on 2009-01-03 14:31 doing5552 閱讀(522) 評論(0) 編輯收藏引用

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輸出

輸出
Hello, World! (basic_string)
Hello, World! (char )
Hello, World! (wchar_t )
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (System::String)

從 System::String 轉換

doing5552

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留言簿(24)

我參與的團隊

隨筆分類(2)

隨筆檔案(73)

news

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積分與排名

最新隨筆

最新評論

閱讀排行榜

評論排行榜

輸出

輸出Hello, World! (basic_string)Hello, World! (char *)Hello, World! (wchar_t *)Hello, World! (_bstr_t)Hello, World! (CComBSTR)Hello, World! (CString)Hello, World! (System::String) 從 System::String 轉換

輸出
Hello, World! (basic_string)
Hello, World! (char )
Hello, World! (wchar_t )
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CString)
Hello, World! (System::String)

從 System::String 轉換