QLocale Class▲

  • Header: QLocale

  • CMake:

    find_package(Qt6 REQUIRED COMPONENTS Core)

    target_link_libraries(mytarget PRIVATE Qt6::Core)

  • qmake: QT += core

  • Group: QLocale is part of i18n, string-processing, Implicitly Shared Classes

Detailed Description▲

QLocale is constructed for a specified language, optional script and territory. It offers various facilities for formatting data as text, localized appropriately, and for reading data out of localized text.

Example:

 
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QLocale egyptian(QLocale::Arabic, QLocale::Egypt);
QString s1 = egyptian.toString(1.571429E+07, 'e');
QString s2 = egyptian.toString(10);

double d = egyptian.toDouble(s1);
int i = egyptian.toInt(s2);

QLocale supports the concept of a default locale, which is determined from the system's locale settings at application startup. The default locale can be changed by calling the static member setDefault(). Setting the default locale has the following effects:

  • If a QLocale object is constructed with the default constructor, it will use the default locale's settings.

  • QString::arg() uses the default locale to format a number when its position specifier in the format string contains an 'L', e.g. "%L1".

The following example illustrates how to use QLocale directly:

 
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bool ok;
double d;

QLocale::setDefault(QLocale::C);      // uses '.' as a decimal point
QLocale cLocale;                      // default-constructed C locale
d = cLocale.toDouble("1234,56", &ok); // ok == false, d == 0
d = cLocale.toDouble("1234.56", &ok); // ok == true,  d == 1234.56

QLocale::setDefault(QLocale::German); // uses ',' as a decimal point
QLocale german;                       // default-constructed German locale
d = german.toDouble("1234,56", &ok);  // ok == true,  d == 1234.56
d = german.toDouble("1234.56", &ok);  // ok == false, d == 0

QLocale::setDefault(QLocale::English);
// Default locale now uses ',' as a group separator.
QString str = QString("%1 %L2 %L3").arg(12345).arg(12345).arg(12345, 0, 16);
// str == "12345 12,345 3039"

An alternative method for constructing a QLocale object is by specifying the locale name.

 
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QLocale korean("ko");
QLocale swiss("de_CH");

This constructor reads the language, script and/or territory from the given name, accepting either uderscore or dash as separator (and ignoring any trailing .codeset or @variant suffix).

For the current keyboard input locale take a look at QInputMethod::locale().

QLocale's data is based on Common Locale Data Repository v40.

Matching combinations of language, script and territory▲

QLocale has data, derived from CLDR, for many combinations of language, script and territory, but not all. If it is constructed with all three of these key values specified (treating AnyLanguage, AnyScript or AnyTerritory as unspecified) and QLocale has data for the given combination, this data is used. Otherwise, QLocale does its best to find a sensible combination of language, script and territory, for which it does have data, that matches those that were specified.

The CLDR provides tables of likely combinations, which are used to fill in any unspecified key or keys; if QLocale has data for the result of such a likely combination, that is used. If no language is specified, and none can be determined from script and territory, or if QLocale has no data for the language, the "C" locale (when reading the keys from a string) or default locale (otherwise) is used.

When QLocale has no data for the keys specified, with likely keys filled in where unspecified, but does have data for the resulting language, a fall-back is sought, based on ig