std::locale::id

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME

 

std::locale

Member types

locale::id

locale::facet

Member functions

locale::locale

locale::~locale

locale::operator=

locale::combine

locale::name

locale::operator==locale::operator!=

locale::operator()

Static member functions

locale::global

locale::classic

 

Defined in header <locale>
class locale::id;

The class std::locale::id provides implementation-specific identification of a locale facet. Each class derived from std::locale::facet must have a public static member named id of type std::locale::id and each std::locale object maintains a list of facets it implements, indexed by their ids.

Facets with the same id belong to the same facet category and replace each other when added to a locale object.

Member functions

(constructor)	constructs a new id (public member function)
operator=	copy assignment operator is deleted (public member function)

Example

The following example shows how to construct a minimal custom facet.

Run this code

#include <iostream>
#include <locale>
 
struct myfacet : std::locale::facet
{
    myfacet(std::size_t refs = 0) : facet(refs) {}
    static std::locale::id id;
};
 
std::locale::id myfacet::id;
 
int main()
{
    std::locale myloc(std::locale(), new myfacet);
    std::cout << "has_facet<myfacet>(myloc) returns " << std::boolalpha
              << std::has_facet<myfacet>(myloc) << '\n';
}

Output:

has_facet<myfacet>(myloc) returns true

See also

facet

the base class for all facet categories: each facet of any category is derived from this type (class)