PluralFormat Class Reference

#include <plurfmt.h>

Inheritance diagram for PluralFormat:
Format UObject UMemory

Public Member Functions

 PluralFormat (UErrorCode &status)
 Creates a new PluralFormat for the default locale.
 PluralFormat (const Locale &locale, UErrorCode &status)
 Creates a new 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 UnicodeString &pattern, UErrorCode &status)
 Creates a new PluralFormat for a given pattern string.
 PluralFormat (const Locale &locale, const UnicodeString &pattern, UErrorCode &status)
 Creates a new 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 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.

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 users 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., paucal 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

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 used locale. The pattern is a sequence of caseKeyword{message} clauses, separated by white space characters. Each clause assigns the message message to the plural case identified by caseKeyword.

You always have to define a message text for the default plural case "<code>other</code>" which is contained in every rule set. If the plural rules of the PluralFormat object do not contain a plural case identified by caseKeyword, U_DEFAULT_KEYWORD_MISSING will be set to status. If you do not specify a message text for a particular plural case, the message text of the plural case "<code>other</code>" gets assigned to this plural case. If you specify more than one message for the same plural case, U_DUPLICATE_KEYWORD will be set to status.
Spaces between caseKeyword and message will be ignored; spaces within message will be preserved.

The message text for a particular plural case may contain other message format patterns. PluralFormat preserves these so that you can use the strings produced by PluralFormat with other formatters. If you are using PluralFormat inside a MessageFormat pattern, MessageFormat will automatically evaluate the resulting format pattern.
Thus, curly braces ({, }) are only allowed in message texts to define a nested format pattern.
The pound sign (#) will be interpreted as the number placeholder in the message text, if it is not contained in curly braces (to preserve NumberFormat patterns). PluralFormat will replace each of those pound signs by the number passed to the format() method. It will be formatted using a NumberFormat for the PluralFormat's locale. If you need special number formatting, you have to explicitly specify a NumberFormat for the PluralFormat to use. Example

 UErrorCode status = U_ZERO_ERROR;
 MessageFormat* msgFmt = new MessageFormat(UnicodeString("{0, plural,
   one{{0, number, C''est #,##0.0#  fichier}} other {Ce sont # fichiers}} dans la liste."),
   Locale("fr"), status);
 if (U_FAILURE(status)) {
     return;
 }
 Formattable args1[] = {(int32_t)0};
 Formattable args2[] = {(int32_t)3};
 FieldPosition ignore(FieldPosition::DONT_CARE);
 UnicodeString result;
 msgFmt->format(args1, 1, result, ignore, status);
 cout << result << endl;
 result.remove();
 msgFmt->format(args2, 1, result, ignore, status);
 cout << result << endl;
 

Produces the output:
C'est 0,0 fichier dans la liste.
Ce sont 3 fichiers dans la liste.

Note:
Currently PluralFormat does not make use of quotes like MessageFormat. If you use plural format strings with MessageFormat and want to use a quote sign "<code>'</code>", you have to write "<code>''</code>". MessageFormat unquotes this pattern and passes the unquoted pattern to PluralFormat. It's a bit trickier if you use nested formats that do quoting. In the example above, we wanted to insert "<code>'</code>" in the number format pattern. Since NumberFormat supports quotes, we had to insert "<code>''</code>". But since MessageFormat unquotes the pattern before it gets passed to PluralFormat, we have to double these quotes, i.e. write "<code>''''</code>".

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 174 of file plurfmt.h.


Constructor & Destructor Documentation

PluralFormat::PluralFormat ( UErrorCode status  ) 

Creates a new 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::PluralFormat ( const Locale locale,
UErrorCode status 
)

Creates a new 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
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
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
PluralFormat::PluralFormat ( const UnicodeString pattern,
UErrorCode status 
)

Creates a new 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::PluralFormat ( const Locale locale,
const UnicodeString pattern,
UErrorCode status 
)

Creates a new 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
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
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
PluralFormat::PluralFormat ( const PluralFormat other  ) 

copy constructor.

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

Destructor.

Stable:
ICU 4.0

Member Function Documentation

void 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* 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 Format.

UnicodeString& 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 Format.

UnicodeString& 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& 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 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 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 PluralFormat::getDynamicClassID (  )  const [virtual]

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

Stable:
ICU 4.0

Implements Format.

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

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

Stable:
ICU 4.0
virtual UBool 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& PluralFormat::operator= ( const PluralFormat other  ) 

Assignment operator.

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

Reimplemented from Format.

virtual UBool 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 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 Format.

void 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, UErrorCode& status).

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.
Stable:
ICU 4.0
void 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& 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:
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Generated on Sat Jan 23 15:17:43 2010 for ICU 4.3.4 by  doxygen 1.6.1