How does visual c ++ convert string types?

This topic demonstrates how to convert various C ++ string types to other strings. The string types that can be converted includeChar *,Wchar_t *, _ Bstr_t, ccombstr, cstring, basic_string, and system. String. In all cases, a copy of the string is created when a string is converted to a new type. Any changes made to the new string will not affect the original string, and vice versa.

Example of conversion from char *

This example shows howChar *Convert to other string types listed above.

// 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 origsize = 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;}

Output

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)

Example of conversion from wchar_t *

This example shows howWchar_t *Convert to other string types listed above.

// 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 origsize = 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;}

Output

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)

Example of conversion from _ bstr_t

This example shows how_ Bstr_tConvert to other string types listed above.

// 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;}

Output

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)

Example of ccombstr Conversion

This example shows howCcombstrConvert to other string types listed above.

// 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;}

Output

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)

Example of cstring Conversion

This example shows howCstringConvert to other string types listed above.

// 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 origsize = 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;}

Output

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)

Example of conversion from basic_string

This example shows howBasic_stringConvert to other string types listed above.

// convert_from_basic_string.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(){    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 origsize = 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;}

Output

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)

Example of conversion from system: String

This example shows howSystem. StringConvert to other string types listed above.

// 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 origsize = 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;}

Output

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