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std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::wstring_convert - cppreference.com

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wstring_convert() : wstring_convert( new Codecvt ) {}

 (1)

explicit wstring_convert( Codecvt* pcvt );

 (2)

wstring_convert( Codecvt* pcvt, state_type state );

 (3)

explicit wstring_convert( const byte_string& byte_err, const wide_string& wide_err = wide_string() );

 (4)

wstring_convert( const std::wstring_convert& ) = delete;

 (5) (since C++14)
 Overload  Data members
 byte_err_string   wide_err_string  cvtptr cvtstate cvtcount
(1) default-initialized  new Codecvt   default-initialized   uninitialized 
(2) pcvt
(3) state
(4) byte_err wide_err new Codecvt state_type()

2,3) If pcvt is a null pointer, the behavior is undefined.

5) The copy constructor is deleted, wstring_convert is not CopyConstructible.

Parameters

pcvt - pointer to the conversion facet
state - initial value of the conversion shift state
byte_err - narrow string to display on errors
wide_err - wide string to display on errors

Example

#include <codecvt>
#include <locale>
#include <utility>

// utility wrapper to adapt locale-bound facets for wstring/wbuffer convert
template<class Facet>
struct deletable_facet : Facet
{
    using Facet::Facet; // inherit constructors
    ~deletable_facet() {}
};

int main()
{
    // UTF-16le / UCS4 conversion
    std::wstring_convert
        <std::codecvt_utf16<char32_t, 0x10ffff, std::little_endian>> u16to32;
    
    // UTF-8 / wide string conversion with custom messages
    std::wstring_convert<std::codecvt_utf8<wchar_t>> u8towide("Error!", L"Error!");
    
    // GB18030 / wide string conversion facet
    using F = deletable_facet<std::codecvt_byname<wchar_t, char, std::mbstate_t>>;
    std::wstring_convert<F> gbtowide(new F("zh_CN.gb18030"));
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2175 C++11 pcvt could be a null pointer the behavior is undefined in this case
LWG 2176 C++11 constructors accepting single argument were implicit made explicit
P0935R0 C++11 the default constructor was explicit made implicit