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]);
}

// Embarcadero C++ Builder 

// convertion string to wstring
string str1 = "hello";
String str2 = str1;         // typedef UnicodeString String;   -> str2 contains now u"hello";

// convertion wstring to string
String str2 = u"hello";
string str1 = UTF8string(str2).c_str();   // -> str1 contains now "hello"

我相信官方的方法仍然是使用codecvt facet(您需要某种语言环境感知的转换)，例如

resultCode = use_facet<codecvt<char, wchar_t, ConversionState> >(locale).
  in(stateVar, scratchbuffer, scratchbufferEnd, from, to, toLimit, curPtr);

或者类似的东西，我没有工作代码。但我不确定现在有多少人使用这种机器，有多少人只是要求内存指针，让ICU或其他库处理血腥的细节。

如果其他人感兴趣的话:我需要一个可以在任何期望使用string或wstring的地方互换使用的类。下面的类convertible_string，基于dk123的解决方案，可以用string, char const*， wstring或wchar_t const*进行初始化，并且可以被赋值或隐式转换为string或wstring(因此可以传递给接受其中任何一种的函数)。

class convertible_string
{
public:
    // default ctor
    convertible_string()
    {}

    /* conversion ctors */
    convertible_string(std::string const& value) : value_(value)
    {}
    convertible_string(char const* val_array) : value_(val_array)
    {}
    convertible_string(std::wstring const& wvalue) : value_(ws2s(wvalue))
    {}
    convertible_string(wchar_t const* wval_array) : value_(ws2s(std::wstring(wval_array)))
    {}

    /* assignment operators */
    convertible_string& operator=(std::string const& value)
    {
        value_ = value;
        return *this;
    }
    convertible_string& operator=(std::wstring const& wvalue)
    {
        value_ = ws2s(wvalue);
        return *this;
    }

    /* implicit conversion operators */
    operator std::string() const { return value_; }
    operator std::wstring() const { return s2ws(value_); }
private:
    std::string value_;
};

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();

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; }