#include <plurfmt.h>
Static Public Member Functions | |
| static U_I18N_API UClassID | getStaticClassID () |
| ICU "poor man's RTTI", returns a UClassID for this class. | |
Friends | |
| class | MessageFormat |
| class | NFRule |
Additional Inherited Members | |
 Protected Member Functions inherited from icu::Format | |
| U_I18N_API void | setLocaleIDs (const char *valid, const char *actual) |
| U_I18N_API | Format () |
| Default constructor for subclass use only. | |
| U_I18N_API | Format (const Format &) |
| U_I18N_API Format & | operator= (const Format &) |
| Static Protected Member Functions inherited from icu::Format | |
| static U_I18N_API void | syntaxError (const UnicodeString &pattern, int32_t pos, UParseError &parseError) |
| Simple function for initializing a UParseError from a UnicodeString. | |
Detailed Description
PluralFormat supports the creation of internationalized messages with plural inflection. It is based on plural selection, i.e. the caller specifies messages for each plural case that can appear in the user's language and the PluralFormat selects the appropriate message based on the number.
The Problem of Plural Forms in Internationalized Messages
Different languages have different ways to inflect plurals. Creating internationalized messages that include plural forms is only feasible when the framework is able to handle plural forms of all languages correctly. ChoiceFormat doesn't handle this well, because it attaches a number interval to each message and selects the message whose interval contains a given number. This can only handle a finite number of intervals. But in some languages, like Polish, one plural case applies to infinitely many intervals (e.g., the plural case applies to numbers ending with 2, 3, or 4 except those ending with 12, 13, or 14). Thus ChoiceFormat is not adequate.
PluralFormat deals with this by breaking the problem into two parts:
-
It uses
PluralRulesthat can define more complex conditions for a plural case than just a single interval. These plural rules define both what plural cases exist in a language, and to which numbers these cases apply. - It provides predefined plural rules for many languages. Thus, the programmer need not worry about the plural cases of a language and does not have to define the plural cases; they can simply use the predefined keywords. The whole plural formatting of messages can be done using localized patterns from resource bundles. For predefined plural rules, see the CLDR Language Plural Rules page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html
Usage of PluralFormat
Note: Typically, plural formatting is done via MessageFormat with a plural argument type, rather than using a stand-alone PluralFormat.
This discussion assumes that you use PluralFormat with a predefined set of plural rules. You can create one using one of the constructors that takes a locale object. To specify the message pattern, you can either pass it to the constructor or set it explicitly using the applyPattern() method. The format() method takes a number object and selects the message of the matching plural case. This message will be returned.
Patterns and Their Interpretation
The pattern text defines the message output for each plural case of the specified locale. Syntax:
pluralStyle = [offsetValue] (selector '{' message '}')+
offsetValue = "offset:" number
selector = explicitValue | keyword
explicitValue = '=' number // adjacent, no white space in between
keyword = [^[[:Pattern_Syntax:][:Pattern_White_Space:]]]+
message: see MessageFormat
Pattern_White_Space between syntax elements is ignored, except between the {curly braces} and their sub-message, and between the '=' and the number of an explicitValue.
There are 6 predefined casekeyword in CLDR/ICU - 'zero', 'one', 'two', 'few', 'many' and 'other'. You always have to define a message text for the default plural case other which is contained in every rule set. If you do not specify a message text for a particular plural case, the message text of the plural case other gets assigned to this plural case.
When formatting, the input number is first matched against the explicitValue clauses. If there is no exact-number match, then a keyword is selected by calling the PluralRules with the input number minus the offset. (The offset defaults to 0 if it is omitted from the pattern string.) If there is no clause with that keyword, then the "other" clauses is returned.
An unquoted pound sign (#) in the selected sub-message itself (i.e., outside of arguments nested in the sub-message) is replaced by the input number minus the offset. The number-minus-offset value is formatted using a NumberFormat for the PluralFormat's locale. If you need special number formatting, you have to use a MessageFormat and explicitly specify a NumberFormat argument. Note: That argument is formatting without subtracting the offset! If you need a custom format and have a non-zero offset, then you need to pass the number-minus-offset value as a separate parameter.
For a usage example, see the MessageFormat class documentation.
Defining Custom Plural Rules
If you need to use PluralFormat with custom rules, you can create a PluralRules object and pass it to PluralFormat's constructor. If you also specify a locale in this constructor, this locale will be used to format the number in the message texts.
For more information about PluralRules, see PluralRules.
ported from Java
- Stable:
- ICU 4.0
Constructor & Destructor Documentation
◆ PluralFormat() [1/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | UErrorCode & | status | ) |
Creates a new cardinal-number PluralFormat for the default locale.
This locale will be used to get the set of plural rules and for standard number formatting.
- Parameters
-
status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [2/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const Locale & | locale, |
| UErrorCode & | status | ||
| ) |
Creates a new cardinal-number PluralFormat for a given locale.
- Parameters
-
locale the PluralFormatwill be configured with rules for this locale. This locale will also be used for standard number formatting.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [3/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const PluralRules & | rules, |
| UErrorCode & | status | ||
| ) |
Creates a new PluralFormat for a given set of rules.
The standard number formatting will be done using the default locale.
- Parameters
-
rules defines the behavior of the PluralFormatobject.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [4/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const Locale & | locale, |
| const PluralRules & | rules, | ||
| UErrorCode & | status | ||
| ) |
Creates a new PluralFormat for a given set of rules.
The standard number formatting will be done using the given locale.
- Parameters
-
locale the default number formatting will be done using this locale. rules defines the behavior of the PluralFormatobject.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [5/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const Locale & | locale, |
| UPluralType | type, | ||
| UErrorCode & | status | ||
| ) |
Creates a new PluralFormat for the plural type.
The standard number formatting will be done using the given locale.
- Parameters
-
locale the default number formatting will be done using this locale. type The plural type (e.g., cardinal or ordinal). status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 50
◆ PluralFormat() [6/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const UnicodeString & | pattern, |
| UErrorCode & | status | ||
| ) |
Creates a new cardinal-number PluralFormat for a given pattern string.
The default locale will be used to get the set of plural rules and for standard number formatting.
- Parameters
-
pattern the pattern for this PluralFormat. errors are returned to status if the pattern is invalid.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [7/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const Locale & | locale, |
| const UnicodeString & | pattern, | ||
| UErrorCode & | status | ||
| ) |
Creates a new cardinal-number PluralFormat for a given pattern string and locale.
The locale will be used to get the set of plural rules and for standard number formatting.
- Parameters
-
locale the PluralFormatwill be configured with rules for this locale. This locale will also be used for standard number formatting.pattern the pattern for this PluralFormat. errors are returned to status if the pattern is invalid.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [8/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const PluralRules & | rules, |
| const UnicodeString & | pattern, | ||
| UErrorCode & | status | ||
| ) |
Creates a new PluralFormat for a given set of rules, a pattern and a locale.
- Parameters
-
rules defines the behavior of the PluralFormatobject.pattern the pattern for this PluralFormat. errors are returned to status if the pattern is invalid.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [9/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const Locale & | locale, |
| const PluralRules & | rules, | ||
| const UnicodeString & | pattern, | ||
| UErrorCode & | status | ||
| ) |
Creates a new PluralFormat for a given set of rules, a pattern and a locale.
- Parameters
-
locale the PluralFormatwill be configured with rules for this locale. This locale will also be used for standard number formatting.rules defines the behavior of the PluralFormatobject.pattern the pattern for this PluralFormat. errors are returned to status if the pattern is invalid.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ PluralFormat() [10/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const Locale & | locale, |
| UPluralType | type, | ||
| const UnicodeString & | pattern, | ||
| UErrorCode & | status | ||
| ) |
Creates a new PluralFormat for a plural type, a pattern and a locale.
- Parameters
-
locale the PluralFormatwill be configured with rules for this locale. This locale will also be used for standard number formatting.type The plural type (e.g., cardinal or ordinal). pattern the pattern for this PluralFormat. errors are returned to status if the pattern is invalid.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 50
◆ PluralFormat() [11/11]
| U_I18N_API icu::PluralFormat::PluralFormat | ( | const PluralFormat & | other | ) |
copy constructor.
- Stable:
- ICU 4.0
◆ ~PluralFormat()
|
virtual |
Destructor.
- Stable:
- ICU 4.0
Member Function Documentation
◆ applyPattern()
| U_I18N_API void icu::PluralFormat::applyPattern | ( | const UnicodeString & | pattern, |
| UErrorCode & | status | ||
| ) |
Sets the pattern used by this plural format.
The method parses the pattern and creates a map of format strings for the plural rules. Patterns and their interpretation are specified in the class description.
- Parameters
-
pattern the pattern for this plural format errors are returned to status if the pattern is invalid. status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ clone()
|
overridevirtual |
Clones this Format object polymorphically.
The caller owns the result and should delete it when done.
- Stable:
- ICU 4.0
Implements icu::Format.
◆ format() [1/8]
|
overridevirtual |
Formats a plural message for a number taken from a Formattable object.
- Parameters
-
obj The object containing a number for which the plural message should be formatted. The object must be of a numeric type. appendTo output parameter to receive result. Result is appended to existing contents. pos On input: an alignment field, if desired. On output: the offsets of the alignment field. status output param filled with success/failure status.
- Returns
- Reference to 'appendTo' parameter.
- Stable:
- ICU 4.0
Implements icu::Format.
◆ format() [2/8]
|
virtual |
Format an object to produce a string.
This is a pure virtual method which subclasses must implement. This method allows polymorphic formatting of Formattable objects. If a subclass of Format receives a Formattable object type it doesn't handle (e.g., if a numeric Formattable is passed to a DateFormat object) then it returns a failing UErrorCode.
- Parameters
-
obj The object to format. appendTo Output parameter to receive result. Result is appended to existing contents. pos On input: an alignment field, if desired. On output: the offsets of the alignment field. status Output param filled with success/failure status.
- Returns
- Reference to 'appendTo' parameter.
- Stable:
- ICU 2.0
Implements icu::Format.
◆ format() [3/8]
|
virtual |
Format an object to produce a string.
Subclasses should override this method. This method allows polymorphic formatting of Formattable objects. If a subclass of Format receives a Formattable object type it doesn't handle (e.g., if a numeric Formattable is passed to a DateFormat object) then it returns a failing UErrorCode.
- Parameters
-
obj The object to format. appendTo Output parameter to receive result. Result is appended to existing contents. posIter On return, can be used to iterate over positions of fields generated by this format call. status Output param filled with success/failure status.
- Returns
- Reference to 'appendTo' parameter.
- Stable:
- ICU 4.4
Reimplemented from icu::Format.
◆ format() [4/8]
| U_I18N_API UnicodeString & icu::Format::format | ( | const Formattable & | obj, |
| UnicodeString & | appendTo, | ||
| UErrorCode & | status | ||
| ) | const |
Formats an object to produce a string.
- Parameters
-
obj The object to format. appendTo Output parameter to receive result. Result is appended to existing contents. status Output parameter filled in with success or failure status.
- Returns
- Reference to 'appendTo' parameter.
- Stable:
- ICU 2.0
◆ format() [5/8]
| U_I18N_API UnicodeString icu::PluralFormat::format | ( | double | number, |
| UErrorCode & | status | ||
| ) | const |
Formats a plural message for a given number.
- Parameters
-
number a number for which the plural message should be formatted for. If no pattern has been applied to this PluralFormat object yet, the formatted number will be returned. status output param set to success or failure code on exit, which must not indicate a failure before the function call.
- Returns
- the string containing the formatted plural message.
- Stable:
- ICU 4.0
◆ format() [6/8]
| U_I18N_API UnicodeString & icu::PluralFormat::format | ( | double | number, |
| UnicodeString & | appendTo, | ||
| FieldPosition & | pos, | ||
| UErrorCode & | status | ||
| ) | const |
Formats a plural message for a given number.
- Parameters
-
number a number for which the plural message should be formatted for. If no pattern has been applied to this PluralFormat object yet, the formatted number will be returned. appendTo output parameter to receive result. result is appended to existing contents. pos On input: an alignment field, if desired. On output: the offsets of the alignment field. status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Returns
- the string containing the formatted plural message.
- Stable:
- ICU 4.0
◆ format() [7/8]
| U_I18N_API UnicodeString icu::PluralFormat::format | ( | int32_t | number, |
| UErrorCode & | status | ||
| ) | const |
Formats a plural message for a given number.
- Parameters
-
number a number for which the plural message should be formatted for. If no pattern has been applied to this PluralFormatobject yet, the formatted number will be returned.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Returns
- the string containing the formatted plural message.
- Stable:
- ICU 4.0
◆ format() [8/8]
| U_I18N_API UnicodeString & icu::PluralFormat::format | ( | int32_t | number, |
| UnicodeString & | appendTo, | ||
| FieldPosition & | pos, | ||
| UErrorCode & | status | ||
| ) | const |
Formats a plural message for a given number.
- Parameters
-
number a number for which the plural message should be formatted for. If no pattern has been applied to this PluralFormatobject yet, the formatted number will be returned.appendTo output parameter to receive result. result is appended to existing contents. pos On input: an alignment field, if desired. On output: the offsets of the alignment field. status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Returns
- the string containing the formatted plural message.
- Stable:
- ICU 4.0
◆ getDynamicClassID()
|
overridevirtual |
ICU "poor man's RTTI", returns a UClassID for the actual class.
- Stable:
- ICU 4.0
Reimplemented from icu::UObject.
◆ getStaticClassID()
|
static |
ICU "poor man's RTTI", returns a UClassID for this class.
- Stable:
- ICU 4.0
◆ operator!=()
|
virtual |
Return true if another object is semantically unequal to this one.
- Parameters
-
other the PluralFormat object to be compared with.
- Returns
- true if other is semantically unequal to this.
- Stable:
- ICU 4.0
◆ operator=()
| U_I18N_API PluralFormat & icu::PluralFormat::operator= | ( | const PluralFormat & | other | ) |
◆ operator==()
|
overridevirtual |
Return true if another object is semantically equal to this one.
- Parameters
-
other the PluralFormat object to be compared with.
- Returns
- true if other is semantically equal to this.
- Stable:
- ICU 4.0
Implements icu::Format.
◆ parseObject()
|
overridevirtual |
This method is not yet supported by PluralFormat.
Before calling, set parse_pos.index to the offset you want to start parsing at in the source. After calling, parse_pos.index is the end of the text you parsed. If error occurs, index is unchanged.
When parsing, leading whitespace is discarded (with a successful parse), while trailing whitespace is left as is.
See Format::parseObject() for more.
- Parameters
-
source The string to be parsed into an object. result Formattable to be set to the parse result. If parse fails, return contents are undefined. parse_pos The position to start parsing at. Upon return this param is set to the position after the last character successfully parsed. If the source is not parsed successfully, this param will remain unchanged.
- Stable:
- ICU 4.0
Implements icu::Format.
◆ setLocale()
| U_I18N_API void icu::PluralFormat::setLocale | ( | const Locale & | locale, |
| UErrorCode & | status | ||
| ) |
Sets the locale used by this PluraFormat object.
Note: Calling this method resets this PluraFormat object, i.e., a pattern that was applied previously will be removed, and the NumberFormat is set to the default number format for the locale. The resulting format behaves the same as one constructed from PluralFormat(const Locale& locale, UPluralType type, UErrorCode& status) with UPLURAL_TYPE_CARDINAL.
- Parameters
-
locale the localeto use to configure the formatter.status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Deprecated:
- ICU 50 This method clears the pattern and might create a different kind of PluralRules instance; use one of the constructors to create a new instance instead.
◆ setNumberFormat()
| U_I18N_API void icu::PluralFormat::setNumberFormat | ( | const NumberFormat * | format, |
| UErrorCode & | status | ||
| ) |
Sets the number format used by this formatter.
You only need to call this if you want a different number format than the default formatter for the locale.
- Parameters
-
format the number format to use. status output param set to success/failure code on exit, which must not indicate a failure before the function call.
- Stable:
- ICU 4.0
◆ toPattern()
| U_I18N_API UnicodeString & icu::PluralFormat::toPattern | ( | UnicodeString & | appendTo | ) |
Returns the pattern from applyPattern() or constructor().
- Parameters
-
appendTo output parameter to receive result. Result is appended to existing contents.
- Returns
- the UnicodeString with inserted pattern.
- Stable:
- ICU 4.0
Friends And Related Symbol Documentation
◆ MessageFormat
|
friend |
◆ NFRule
The documentation for this class was generated from the following file:
- i18n/unicode/plurfmt.h
