c++ - ‘virtual char std::ctype<wchar_t>::do_narrow(wchar_t, char) const’ protected

Question

我正在尝试使用语言环境方面将 wstring 转换为字符串，但我遇到了以下错误:

test_facet.cpp: In function ‘int main()’:
test_facet.cpp:14: error: invalid initialization of reference of type ‘std::ctype<wchar_t>&’ from expression of type ‘const std::ctype<wchar_t>’
/usr/include/c++/4.4/bits/locale_facets.h:1430: error: ‘virtual char std::ctype<wchar_t>::do_narrow(wchar_t, char) const’ is protected
test_facet.cpp:16: error: within this context

来源:

#include <iostream>
#include <string>
#include <locale>
#include <algorithm>

using namespace std;

int main()
{
 locale loc("");
 std::wstring Str = L"ěščřžýáíé";
 std::string Str2;
 ctype<wchar_t> &ct = std::use_facet<std::ctype<wchar_t> >(loc);
 for(std::wstring::const_iterator It = Str.begin(); It < Str.end(); ++It)
   ct.do_narrow(*It, 'X' );
 std::cout << Str2 <<std::endl;
}

谁能告诉我，我做错了什么？

谢谢

Answer 1

2 件事:

1) use_facet 返回对 const 的引用，因此您不能将其分配给非 const 引用。所以将 ct 声明为:

 const ctype<wchar_t> &ct = ....

2) 如第二条错误消息所述，do_narrow 受到保护，外部调用者无法访问它。请改用 narrow，它是公开的。