问题是如何将wstring转换为字符串?

我还有一个例子:

#include <string>
#include <iostream>

int main()
{
    std::wstring ws = L"Hello";
    std::string s( ws.begin(), ws.end() );

  //std::cout <<"std::string =     "<<s<<std::endl;
    std::wcout<<"std::wstring =    "<<ws<<std::endl;
    std::cout <<"std::string =     "<<s<<std::endl;
}

带注释的输出为:

std::string =     Hello
std::wstring =    Hello
std::string =     Hello

但是without只是:

std::wstring =    Hello

这个例子中有什么问题吗?我可以像上面那样进行转换吗?

EDIT

新例子(考虑到一些答案)是

#include <string>
#include <iostream>
#include <sstream>
#include <locale>

int main()
{
    setlocale(LC_CTYPE, "");

    const std::wstring ws = L"Hello";
    const std::string s( ws.begin(), ws.end() );

    std::cout<<"std::string =     "<<s<<std::endl;
    std::wcout<<"std::wstring =    "<<ws<<std::endl;

    std::stringstream ss;
    ss << ws.c_str();
    std::cout<<"std::stringstream =     "<<ss.str()<<std::endl;
}

输出结果为:

std::string =     Hello
std::wstring =    Hello
std::stringstream =     0x860283c

因此,不能使用stringstream将wstring转换为string。


当前回答

你也可以直接使用ctype facet的narrow方法:

#include <clocale>
#include <locale>
#include <string>
#include <vector>

inline std::string narrow(std::wstring const& text)
{
    std::locale const loc("");
    wchar_t const* from = text.c_str();
    std::size_t const len = text.size();
    std::vector<char> buffer(len + 1);
    std::use_facet<std::ctype<wchar_t> >(loc).narrow(from, from + len, '_', &buffer[0]);
    return std::string(&buffer[0], &buffer[len]);
}

其他回答

我使用下面的wstring转换为字符串。

std::string strTo;
char *szTo = new char[someParam.length() + 1];
szTo[someParam.size()] = '\0';
WideCharToMultiByte(CP_ACP, 0, someParam.c_str(), -1, szTo, (int)someParam.length(), NULL, NULL);
strTo = szTo;
delete szTo;

而不是包括locale和所有那些花哨的东西,如果你知道为FACT你的字符串是可转换的,只需这样做:

#include <iostream>
#include <string>

using namespace std;

int main()
{
  wstring w(L"bla");
  string result;
  for(char x : w)
    result += x;

  cout << result << '\n';
}

这里有一个活生生的例子

代码有两个问题:

The conversion in const std::string s( ws.begin(), ws.end() ); is not required to correctly map the wide characters to their narrow counterpart. Most likely, each wide character will just be typecast to char. The resolution to this problem is already given in the answer by kem and involves the narrow function of the locale's ctype facet. You are writing output to both std::cout and std::wcout in the same program. Both cout and wcout are associated with the same stream (stdout) and the results of using the same stream both as a byte-oriented stream (as cout does) and a wide-oriented stream (as wcout does) are not defined. The best option is to avoid mixing narrow and wide output to the same (underlying) stream. For stdout/cout/wcout, you can try switching the orientation of stdout when switching between wide and narrow output (or vice versa): #include <iostream> #include <stdio.h> #include <wchar.h> int main() { std::cout << "narrow" << std::endl; fwide(stdout, 1); // switch to wide std::wcout << L"wide" << std::endl; fwide(stdout, -1); // switch to narrow std::cout << "narrow" << std::endl; fwide(stdout, 1); // switch to wide std::wcout << L"wide" << std::endl; }

我花了很多悲伤的日子,试图为c++ 17找到一种方法来做到这一点,它已经弃用了code_cvt facet,这是我通过组合来自几个不同来源的代码所能想到的最好的方法:

setlocale( LC_ALL, "en_US.UTF-8" ); //Invoked in main()

std::string wideToMultiByte( std::wstring const & wideString )
{
     std::string ret;
     std::string buff( MB_CUR_MAX, '\0' );

     for ( wchar_t const & wc : wideString )
     {
         int mbCharLen = std::wctomb( &buff[ 0 ], wc );

         if ( mbCharLen < 1 ) { break; }

         for ( int i = 0; i < mbCharLen; ++i ) 
         { 
             ret += buff[ i ]; 
         }
     }

     return ret;
 }

 std::wstring multiByteToWide( std::string const & multiByteString )
 {
     std::wstring ws( multiByteString.size(), L' ' );
     ws.resize( 
         std::mbstowcs( &ws[ 0 ], 
             multiByteString.c_str(), 
             multiByteString.size() ) );

     return ws;
 }

我在Windows 10上测试了这段代码,至少就我的目的而言,它似乎运行良好。如果这没有考虑到你可能需要处理的一些疯狂的边缘情况,请不要对我进行私刑,我相信有更多经验的人可以改进这一点!: -)

此外,在该表扬的地方表扬:

适用于wideToMultiByte()

复制multiByteToWide

在写这个答案的时候,第一个谷歌搜索“转换字符串wstring”会让你进入这个页面。我的回答展示了如何将字符串转换为wstring,虽然这不是实际的问题,我应该删除这个答案,但这被认为是糟糕的形式。您可能希望跳转到此StackOverflow答案,该答案现在的排名高于此页面。


这是一种将字符串,wstring和混合字符串常量组合到wstring的方法。使用wstringstream类。

#include <sstream>

std::string narrow = "narrow";
std::wstring wide = "wide";

std::wstringstream cls;
cls << " abc " << narrow.c_str() << L" def " << wide.c_str();
std::wstring total= cls.str();