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MessageFormat Class Reference

Provides means to produce concatenated messages in language-neutral way. More...

#include <msgfmt.h>

Inheritance diagram for MessageFormat:

Format

Public Types

enum  EFormatNumber { kMaxFormat = 10 }

Public Methods

 MessageFormat (const UnicodeString &pattern, UErrorCode &status)
 Construct a new MessageFormat using the given pattern. More...

 MessageFormat (const UnicodeString &pattern, const Locale &newLocale, UErrorCode &success)
 Constructor that allows locale specification. More...

 MessageFormat (const UnicodeString &pattern, const Locale &newLocale, UParseError &parseError, UErrorCode &success)
 Constructor that allows locale specification. More...

 MessageFormat (const MessageFormat &)
 Copy constructor. More...

const MessageFormat & operator= (const MessageFormat &)
 Assignment operator. More...

virtual ~MessageFormat ()
 Destructor. More...

virtual Formatclone (void) const
 Clone this Format object polymorphically. More...

virtual UBool operator== (const Format &other) const
 Return true if the given Format objects are semantically equal. More...

virtual void setLocale (const Locale &theLocale)
 Sets the locale. More...

virtual const Locale & getLocale (void) const
 Gets the locale. More...

virtual void applyPattern (const UnicodeString &pattern, UErrorCode &status)
 Apply the given pattern string to this message format. More...

virtual void applyPattern (const UnicodeString &pattern, UParseError &parseError, UErrorCode &status)
 Sets the pattern. More...

virtual UnicodeStringtoPattern (UnicodeString &result) const
 Gets the pattern. More...

virtual void adoptFormats (Format **formatsToAdopt, int32_t count)
 Sets formats to use on parameters. More...

virtual void setFormats (const Format **newFormats, int32_t cnt)
 Sets formats to use on parameters. More...

virtual void adoptFormat (int32_t formatNumber, Format *formatToAdopt)
 Sets formats individually to use on parameters. More...

virtual void setFormat (int32_t variable, const Format &newFormat)
 Sets formats individually to use on parameters. More...

virtual const Format ** getFormats (int32_t &count) const
 Gets formats that were set with setFormats. More...

UnicodeStringformat (const Formattable *source, int32_t count, UnicodeString &result, FieldPosition &ignore, UErrorCode &success) const
 Returns pattern with formatted objects. More...

virtual UnicodeStringformat (const Formattable &obj, UnicodeString &toAppendTo, FieldPosition &pos, UErrorCode &status) const
 Format an object to produce a message. More...

UnicodeStringformat (const Formattable &obj, UnicodeString &result, UErrorCode &status) const
 Redeclared Format method. More...

virtual Formattableparse (const UnicodeString &source, ParsePosition &status, int32_t &count) const
 Parses the string. More...

virtual Formattableparse (const UnicodeString &source, int32_t &count, UErrorCode &status) const
 Parses the string. More...

virtual void parseObject (const UnicodeString &source, Formattable &result, ParsePosition &parse_pos) const
 Parse a string to produce an object. More...

virtual UClassID getDynamicClassID (void) const
 Returns a unique class ID POLYMORPHICALLY. More...

const Formattable::TypegetFormatTypeList (int32_t &listCount)
 Returns array of formattable types in the parsed pattern for use in C API. More...


Static Public Methods

UnicodeStringformat (const UnicodeString &pattern, const Formattable *arguments, int32_t count, UnicodeString &result, UErrorCode &success)
 Convenience routine. More...

UClassID getStaticClassID (void)
 Return the class ID for this class. More...


Detailed Description

Provides means to produce concatenated messages in language-neutral way.

Use this for all concatenations that show up to end users.

Takes a set of objects, formats them, then inserts the formatted strings into the pattern at the appropriate places.

Here are some examples of usage: Example 1:

 
     UErrorCode success = U_ZERO_ERROR;
     GregorianCalendar cal(success);
     Formattable arguments[] = {
         7L,
         Formattable( (Date) cal.getTime(success), Formattable::kIsDate),
         "a disturbance in the Force"
     };

     UnicodeString result;
     MessageFormat::format(
          "At {1,time} on {1,date}, there was {2} on planet {0,number}.",
          arguments, 3, result, success );

     cout << "result: " << result << endl;
     //<output>: At 4:34:20 PM on 23-Mar-98, there was a disturbance
     //             in the Force on planet 7.
Typically, the message format will come from resources, and the arguments will be dynamically set at runtime.

Example 2:

  
     success = U_ZERO_ERROR;
     Formattable testArgs[] = {3L, "MyDisk"};

     MessageFormat* form = new MessageFormat(
         "The disk \"{1}\" contains {0} file(s).", success );

     UnicodeString string;
     FieldPosition fpos = 0;
     cout &lt;&lt; "format: " &lt;&lt; form->format(testArgs, 2, string, fpos, success ) &lt;&lt; endl;

     // output, with different testArgs:
     // output: The disk "MyDisk" contains 0 file(s).
     // output: The disk "MyDisk" contains 1 file(s).
     // output: The disk "MyDisk" contains 1,273 file(s).
     delete form;

The pattern is of the following form. Legend:

 
       {optional item}
       (group that may be repeated)*
Do not confuse optional items with items inside quotes braces, such as this: "{". Quoted braces are literals.
  
       messageFormatPattern := string ( "{" messageFormatElement "}" string )*

       messageFormatElement := argument { "," elementFormat }

       elementFormat := "time" { "," datetimeStyle }
                      | "date" { "," datetimeStyle }
                      | "number" { "," numberStyle }
                      | "choice" "," choiceStyle

       datetimeStyle := "short"
                      | "medium"
                      | "long"
                      | "full"
                      | dateFormatPattern

       numberStyle :=   "currency"
                      | "percent"
                      | "integer"
                      | numberFormatPattern

       choiceStyle :=   choiceFormatPattern
If there is no elementFormat, then the argument must be a string, which is substituted. If there is no dateTimeStyle or numberStyle, then the default format is used (e.g. NumberFormat.getInstance(), DateFormat.getDefaultTime() or DateFormat.getDefaultDate(). For a ChoiceFormat, the pattern must always be specified, since there is no default.

In strings, single quotes can be used to quote the "{" sign if necessary. A real single quote is represented by ''. Inside a messageFormatElement, quotes are [not] removed. For example, {1,number,$'#',##} will produce a number format with the pound-sign quoted, with a result such as: "$#31,45".

If a pattern is used, then unquoted braces in the pattern, if any, must match: that is, "ab {0} de" and "ab '}' de" are ok, but "ab {0'}' de" and "ab } de" are not.

The argument is a number from 0 to 9, which corresponds to the arguments presented in an array to be formatted.

It is ok to have unused arguments in the array. With missing arguments or arguments that are not of the right class for the specified format, a failing UErrorCode result is set.

For more sophisticated patterns, you can use a ChoiceFormat to get output such as:

 
     UErrorCode success = U_ZERO_ERROR;
     MessageFormat* form = new MessageFormat("The disk \"{1}\" contains {0}.", success);
     double filelimits[] = {0,1,2};
     UnicodeString filepart[] = {"no files","one file","{0,number} files"};
     ChoiceFormat* fileform = new ChoiceFormat(filelimits, filepart, 3);
     form->setFormat(1, *fileform); // NOT zero, see below

     Formattable testArgs[] = {1273L, "MyDisk"};

     UnicodeString string;
     FieldPosition fpos = 0;
     cout << form->format(testArgs, 2, string, fpos, success) << endl;

     // output, with different testArgs
     // output: The disk "MyDisk" contains no files.
     // output: The disk "MyDisk" contains one file.
     // output: The disk "MyDisk" contains 1,273 files.
You can either do this programmatically, as in the above example, or by using a pattern (see ChoiceFormat for more information) as in:
 
    form->applyPattern(
      "There {0,choice,0#are no files|1#is one file|1<are {0,number,integer} files}.");

[Note:] As we see above, the string produced by a ChoiceFormat in MessageFormat is treated specially; occurances of '{' are used to indicated subformats, and cause recursion. If you create both a MessageFormat and ChoiceFormat programmatically (instead of using the string patterns), then be careful not to produce a format that recurses on itself, which will cause an infinite loop.

[Note:] Formats are numbered by order of variable in the string. This is [not] the same as the argument numbering!

 
    For example: with "abc{2}def{3}ghi{0}...",

    format0 affects the first variable {2}
    format1 affects the second variable {3}
    format2 affects the second variable {0}
and so on.


Constructor & Destructor Documentation

MessageFormat::MessageFormat const UnicodeString   pattern,
UErrorCode   status
 

Construct a new MessageFormat using the given pattern.

Parameters:
pattern  Pattern used to construct object.
status  Output param to receive success code. If the pattern cannot be parsed, set to failure code. @stable

MessageFormat::MessageFormat const UnicodeString   pattern,
const Locale &    newLocale,
UErrorCode   success
 

Constructor that allows locale specification.

Parameters:
pattern  Pattern used to construct object.
newLocale  The locale to use for formatting dates and numbers.
status  Output param to receive success code. If the pattern cannot be parsed, set to failure code. @stable

MessageFormat::MessageFormat const UnicodeString   pattern,
const Locale &    newLocale,
UParseError &    parseError,
UErrorCode   success
 

Constructor that allows locale specification.

Parameters:
pattern  Pattern used to construct object.
newLocale  The locale to use for formatting dates and numbers.
parseError  Struct to recieve information on position of error if an error is encountered
status  Output param to receive success code. If the pattern cannot be parsed, set to failure code. @stable

MessageFormat::MessageFormat const MessageFormat &   
 

Copy constructor.

@stable

virtual MessageFormat::~MessageFormat   [virtual]
 

Destructor.

@stable


Member Function Documentation

virtual void MessageFormat::adoptFormat int32_t    formatNumber,
Format   formatToAdopt
[virtual]
 

Sets formats individually to use on parameters.

See the class description about format numbering. The caller should not delete the Format object after this call. @draft HSYS: possible semantic change on limitation of the size of array

virtual void MessageFormat::adoptFormats Format **    formatsToAdopt,
int32_t    count
[virtual]
 

Sets formats to use on parameters.

See the class description about format numbering. The caller should not delete the Format objects after this call. @draft HSYS: possible semantic change on limitation of the size of array

virtual void MessageFormat::applyPattern const UnicodeString   pattern,
UParseError &    parseError,
UErrorCode   status
[virtual]
 

Sets the pattern.

Parameters:
pattern  The pattern to be applied.
parseError  Struct to recieve information on position of error if an error is encountered
status  Output param set to success/failure code on exit. If the pattern is invalid, this will be set to a failure result. @draft

virtual void MessageFormat::applyPattern const UnicodeString   pattern,
UErrorCode   status
[virtual]
 

Apply the given pattern string to this message format.

Parameters:
pattern  The pattern to be applied.
status  Output param set to success/failure code on exit. If the pattern is invalid, this will be set to a failure result. @stable

virtual Format* MessageFormat::clone void    const [virtual]
 

Clone this Format object polymorphically.

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

Implements Format.

UnicodeString & MessageFormat::format const Formattable   obj,
UnicodeString   result,
UErrorCode   status
const [inline]
 

Redeclared Format method.

@stable

Reimplemented from Format.

virtual UnicodeString& MessageFormat::format const Formattable   obj,
UnicodeString   toAppendTo,
FieldPosition   pos,
UErrorCode   status
const [virtual]
 

Format an object to produce a message.

This method handles Formattable objects of type kArray. If the Formattable object type is not of type kArray, then it returns a failing UErrorCode.

Parameters:
obj  The object to format
toAppendTo  Where the text is to be appended
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:
The value passed in as toAppendTo (this allows chaining, as with UnicodeString::append()) @stable

Implements Format.

UnicodeString& MessageFormat::format const UnicodeString   pattern,
const Formattable   arguments,
int32_t    count,
UnicodeString   result,
UErrorCode   success
[static]
 

Convenience routine.

Avoids explicit creation of MessageFormat, but doesn't allow future optimizations. @stable

UnicodeString& MessageFormat::format const Formattable   source,
int32_t    count,
UnicodeString   result,
FieldPosition   ignore,
UErrorCode   success
const
 

Returns pattern with formatted objects.

Does not take ownership of the Formattable* array; just reads it and uses it to generate the format string.

Parameters:
source  An array of objects to be formatted & substituted.
result  Where text is appended.
ignore  No useful status is returned. @stable

UClassID MessageFormat::getDynamicClassID void    const [inline, virtual]
 

Returns a unique class ID POLYMORPHICALLY.

Pure virtual override. This method is to implement a simple version of RTTI, since not all C++ compilers support genuine RTTI. Polymorphic operator==() and clone() methods call this method.

Returns:
The class ID for this object. All objects of a given class have the same class ID. Objects of other classes have different class IDs. @stable

Implements Format.

virtual const Format** MessageFormat::getFormats int32_t &    count const [virtual]
 

Gets formats that were set with setFormats.

See the class description about format numbering. @draft HSYS: possible semantic change on limitation of the size of array

const Formattable::Type* MessageFormat::getFormatTypeList int32_t &    listCount [inline]
 

Returns array of formattable types in the parsed pattern for use in C API.

Parameters:
count  Output parameter to receive the size of array
Returns:
The array of formattable types in the pattern

For internal use only.

virtual const Locale& MessageFormat::getLocale void    const [virtual]
 

Gets the locale.

This locale is used for fetching default number or date format information. @stable

UClassID MessageFormat::getStaticClassID void    [inline, static]
 

Return the class ID for this class.

This is useful only for comparing to a return value from getDynamicClassID(). For example:

 .   Base* polymorphic_pointer = createPolymorphicObject();
 .   if (polymorphic_pointer->getDynamicClassID() ==
 .      Derived::getStaticClassID()) ...
 
Returns:
The class ID for all objects of this class. @stable

const MessageFormat& MessageFormat::operator= const MessageFormat &   
 

Assignment operator.

@stable

virtual UBool MessageFormat::operator== const Format   other const [virtual]
 

Return true if the given Format objects are semantically equal.

Objects of different subclasses are considered unequal. @stable

Implements Format.

virtual Formattable* MessageFormat::parse const UnicodeString   source,
int32_t &    count,
UErrorCode   status
const [virtual]
 

Parses the string.

Does not yet handle recursion (where the substituted strings contain {n} references.)

Parameters:
source  String to be parsed.
count  Output param to receive size of returned array.
status  Output param to receive success/error code.
Returns:
Array of Formattable objects, with length 'count', owned by the caller. @stable

virtual Formattable* MessageFormat::parse const UnicodeString   source,
ParsePosition   status,
int32_t &    count
const [virtual]
 

Parses the string.

Caveats: The parse may fail in a number of circumstances. For example:

If one of the arguments does not occur in the pattern.

If the format of an argument is loses information, such as with a choice format where a large number formats to "many".

Does not yet handle recursion (where the substituted strings contain {n} references.)

Will not always find a match (or the correct match) if some part of the parse is ambiguous. For example, if the pattern "{1},{2}" is used with the string arguments {"a,b", "c"}, it will format as "a,b,c". When the result is parsed, it will return {"a", "b,c"}.

If a single argument is formatted twice in the string, then the later parse wins.

Parameters:
source  String to be parsed.
status  On input, starting position for parse. On output, final position after parse.
count  Output param to receive size of returned array.
Returns:
Array of Formattable objects, with length 'count', owned by the caller. @stable

virtual void MessageFormat::parseObject const UnicodeString   source,
Formattable   result,
ParsePosition   parse_pos
const [virtual]
 

Parse a string to produce an object.

This methods handles parsing of message strings into arrays of Formattable objects. Does not yet handle recursion (where the substituted strings contain n references.)

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 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.
Returns:
A newly created Formattable* object, or NULL on failure. The caller owns this and should delete it when done. @stable

Implements Format.

virtual void MessageFormat::setFormat int32_t    variable,
const Format   newFormat
[virtual]
 

Sets formats individually to use on parameters.

See the class description about format numbering. @stable

virtual void MessageFormat::setFormats const Format **    newFormats,
int32_t    cnt
[virtual]
 

Sets formats to use on parameters.

See the class description about format numbering. @draft HSYS: possible semantic change on limitation of the size of array

virtual void MessageFormat::setLocale const Locale &    theLocale [virtual]
 

Sets the locale.

This locale is used for fetching default number or date format information. @stable

virtual UnicodeString& MessageFormat::toPattern UnicodeString   result const [virtual]
 

Gets the pattern.

See the class description. @stable


The documentation for this class was generated from the following file:
Generated on Tue Mar 5 06:26:22 2002 for ICU 2.0 by doxygen1.2.14 written by Dimitri van Heesch, © 1997-2002