icu::PluralFormat Class Reference

#include <plurfmt.h>

Inheritance diagram for icu::PluralFormat:
icu::Format icu::UObject icu::UMemory

Data Structures

class  PluralSelector
class  PluralSelectorAdapter

Public Member Functions

 PluralFormat (UErrorCode &status)
 Creates a new cardinal-number PluralFormat for the default locale.
 PluralFormat (const Locale &locale, UErrorCode &status)
 Creates a new cardinal-number PluralFormat for a given locale.
 PluralFormat (const PluralRules &rules, UErrorCode &status)
 Creates a new PluralFormat for a given set of rules.
 PluralFormat (const Locale &locale, const PluralRules &rules, UErrorCode &status)
 Creates a new PluralFormat for a given set of rules.
 PluralFormat (const Locale &locale, UPluralType type, UErrorCode &status)
 Creates a new PluralFormat for the plural type.
 PluralFormat (const UnicodeString &pattern, UErrorCode &status)
 Creates a new cardinal-number PluralFormat for a given pattern string.
 PluralFormat (const Locale &locale, const UnicodeString &pattern, UErrorCode &status)
 Creates a new cardinal-number PluralFormat for a given pattern string and locale.
 PluralFormat (const PluralRules &rules, const UnicodeString &pattern, UErrorCode &status)
 Creates a new PluralFormat for a given set of rules, a pattern and a locale.
 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.
 PluralFormat (const Locale &locale, UPluralType type, const UnicodeString &pattern, UErrorCode &status)
 Creates a new PluralFormat for a plural type, a pattern and a locale.
 PluralFormat (const PluralFormat &other)
 copy constructor.
virtual ~PluralFormat ()
 Destructor.
void applyPattern (const UnicodeString &pattern, UErrorCode &status)
 Sets the pattern used by this plural format.
UnicodeString format (int32_t number, UErrorCode &status) const
 Formats a plural message for a given number.
UnicodeString format (double number, UErrorCode &status) const
 Formats a plural message for a given number.
UnicodeStringformat (int32_t number, UnicodeString &appendTo, FieldPosition &pos, UErrorCode &status) const
 Formats a plural message for a given number.
UnicodeStringformat (double number, UnicodeString &appendTo, FieldPosition &pos, UErrorCode &status) const
 Formats a plural message for a given number.
void setLocale (const Locale &locale, UErrorCode &status)
 Sets the locale used by this PluraFormat object.
void setNumberFormat (const NumberFormat *format, UErrorCode &status)
 Sets the number format used by this formatter.
PluralFormatoperator= (const PluralFormat &other)
 Assignment operator.
virtual UBool operator== (const Format &other) const
 Return true if another object is semantically equal to this one.
virtual UBool operator!= (const Format &other) const
 Return true if another object is semantically unequal to this one.
virtual Formatclone (void) const
 Clones this Format object polymorphically.
UnicodeStringformat (const Formattable &obj, UnicodeString &appendTo, FieldPosition &pos, UErrorCode &status) const
 Redeclared Format method.
UnicodeStringtoPattern (UnicodeString &appendTo)
 Returns the pattern from applyPattern() or constructor().
virtual void parseObject (const UnicodeString &source, Formattable &result, ParsePosition &parse_pos) const
 This method is not yet supported by PluralFormat.
virtual UClassID getDynamicClassID () const
 ICU "poor man's RTTI", returns a UClassID for the actual class.

Static Public Member Functions

static UClassID getStaticClassID (void)
 ICU "poor man's RTTI", returns a UClassID for this class.

Friends

class MessageFormat

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:

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

Definition at line 147 of file plurfmt.h.


Constructor & Destructor Documentation

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
icu::PluralFormat::PluralFormat ( const Locale locale,
UErrorCode status 
)

Creates a new cardinal-number PluralFormat for a given locale.

Parameters:
locale the PluralFormat will 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
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 PluralFormat object.
status output param set to success/failure code on exit, which must not indicate a failure before the function call.
Stable:
ICU 4.0
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 PluralFormat object.
status output param set to success/failure code on exit, which must not indicate a failure before the function call.
Stable:
ICU 4.0
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.
Draft:
This API may be changed in the future versions and was introduced in ICU 50
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
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 PluralFormat will 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
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 PluralFormat object.
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
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 PluralFormat will be configured with rules for this locale. This locale will also be used for standard number formatting.
rules defines the behavior of the PluralFormat object.
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
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 PluralFormat will 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.
Draft:
This API may be changed in the future versions and was introduced in ICU 50
icu::PluralFormat::PluralFormat ( const PluralFormat other  ) 

copy constructor.

Stable:
ICU 4.0
virtual icu::PluralFormat::~PluralFormat (  )  [virtual]

Destructor.

Stable:
ICU 4.0

Member Function Documentation

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
virtual Format* icu::PluralFormat::clone ( void   )  const [virtual]

Clones this Format object polymorphically.

The caller owns the result and should delete it when done.

Stable:
ICU 4.0

Implements icu::Format.

UnicodeString& icu::PluralFormat::format ( const Formattable obj,
UnicodeString appendTo,
FieldPosition pos,
UErrorCode status 
) const [virtual]

Redeclared Format method.

Parameters:
obj The object to be formatted into a string.
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.

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
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 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
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
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 PluralFormat object 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
virtual UClassID icu::PluralFormat::getDynamicClassID (  )  const [virtual]

ICU "poor man's RTTI", returns a UClassID for the actual class.

Stable:
ICU 4.0

Implements icu::UObject.

static UClassID icu::PluralFormat::getStaticClassID ( void   )  [static]

ICU "poor man's RTTI", returns a UClassID for this class.

Stable:
ICU 4.0
virtual UBool icu::PluralFormat::operator!= ( const Format other  )  const [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
PluralFormat& icu::PluralFormat::operator= ( const PluralFormat other  ) 

Assignment operator.

Parameters:
other the PluralFormat object to copy from.
Stable:
ICU 4.0

Reimplemented from icu::Format.

virtual UBool icu::PluralFormat::operator== ( const Format other  )  const [virtual]

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
virtual void icu::PluralFormat::parseObject ( const UnicodeString source,
Formattable result,
ParsePosition parse_pos 
) const [virtual]

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.

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 locale to 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.
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
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

The documentation for this class was generated from the following file:

Generated on 25 Nov 2014 for ICU 50.1.2 by  doxygen 1.6.1