* A MessageFormat contains an array of subformats arranged * within a template string. Together, the subformats and * template string determine how the MessageFormat will operate during * formatting and parsing. *
* Typically, both the subformats and the template string are * specified at once in a pattern. By using different * patterns for different locales, messages may be localized. *
* During formatting, the MessageFormat takes an array of arguments * and produces a user-readable string. Each argument is a * Formattable object; they may be passed in in an array, or as a * single Formattable object which itself contains an array. Each * argument is matched up with its corresponding subformat, which then * formats it into a string. The resultant strings are then assembled * within the string template of the MessageFormat to produce the * final output string. *
* During parsing, an input string is matched against the string * template of the MessageFormat to produce an array of Formattable * objects. Plain text of the template string is matched directly * against intput text. At each position in the template string where * a subformat is located, the subformat is called to parse the * corresponding segment of input text to produce an output argument. * In this way, an array of arguments is created which together * constitute the parse result. *
* Parsing may fail or produce unexpected results in a number of * circumstances. *
* Example 1: *
* \code
* 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;
* //
* Typically, the message format will come from resources, and the
* arguments will be dynamically set at runtime.
* * Example 2: *
* \code
* success = U_ZERO_ERROR;
* Formattable testArgs[] = {3L, "MyDisk"};
*
* MessageFormat form(
* "The disk \"{1}\" contains {0} file(s).", success );
*
* UnicodeString string;
* FieldPosition fpos = 0;
* cout << "format: " << form.format(testArgs, 2, string, fpos, success ) << 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).
* \endcode
*
*
* The pattern is of the following form. Legend:
*
* \code
* {optional item}
* (group that may be repeated)*
* \endcode
*
* Do not confuse optional items with items inside quotes braces, such
* as this: "{". Quoted braces are literals.
*
* \code
* messageFormatPattern := string ( "{" messageFormatElement "}" string )*
*
* messageFormatElement := argumentIndex { "," elementFormat }
*
* elementFormat := "time" { "," datetimeStyle }
* | "date" { "," datetimeStyle }
* | "number" { "," numberStyle }
* | "choice" "," choiceStyle
*
* datetimeStyle := "short"
* | "medium"
* | "long"
* | "full"
* | dateFormatPattern
*
* numberStyle := "currency"
* | "percent"
* | "integer"
* | numberFormatPattern
*
* choiceStyle := choiceFormatPattern
* \endcode
*
* 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::createInstance(),
* DateFormat::createTimeInstance(DateFormat::kDefault, ...) or DateFormat::createDateInstance(DateFormat::kDefault, ...). For
* a ChoiceFormat, the pattern must always be specified, since there
* is no default.
* * In strings, single quotes can be used to quote syntax characters. * A literal single quote is represented by '', both within and outside * of single-quoted segments. 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 argumentIndex is a non-negative integer, which corresponds to the * index of the arguments presented in an array to be formatted. The * first argument has argumentIndex 0. *
* It is acceptable 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: *
* \code
* UErrorCode success = U_ZERO_ERROR;
* MessageFormat* form("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.
* \endcode
*
* You can either do this programmatically, as in the above example,
* or by using a pattern (see ChoiceFormat for more information) as in:
*
* \code
* form.applyPattern(
* "There {0,choice,0#are no files|1#is one file|1
*
* Note: As we see above, the string produced by a ChoiceFormat in
* MessageFormat is treated specially; occurences 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:Subformats are numbered by their order in the pattern.
* This is not the same as the argumentIndex.
*
* \code
* 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}
* \endcode
*
*/
class U_I18N_API MessageFormat : public Format {
public:
/**
* Enum type for kMaxFormat.
* @obsolete ICU 3.0. The 10-argument limit was removed as of ICU 2.6,
* rendering this enum type obsolete.
*/
enum EFormatNumber {
/**
* The maximum number of arguments.
* @obsolete ICU 3.0. The 10-argument limit was removed as of ICU 2.6,
* rendering this constant obsolete.
*/
kMaxFormat = 10
};
/**
* Constructs a new MessageFormat using the given pattern and the
* default locale.
*
* @param pattern Pattern used to construct object.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @stable ICU 2.0
*/
MessageFormat(const UnicodeString& pattern,
UErrorCode &status);
/**
* Constructs a new MessageFormat using the given pattern and locale.
* @param pattern Pattern used to construct object.
* @param newLocale The locale to use for formatting dates and numbers.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @stable ICU 2.0
*/
MessageFormat(const UnicodeString& pattern,
const Locale& newLocale,
UErrorCode& status);
/**
* Constructs a new MessageFormat using the given pattern and locale.
* @param pattern Pattern used to construct object.
* @param newLocale The locale to use for formatting dates and numbers.
* @param parseError Struct to recieve information on position
* of error within the pattern.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @stable ICU 2.0
*/
MessageFormat(const UnicodeString& pattern,
const Locale& newLocale,
UParseError& parseError,
UErrorCode& status);
/**
* Constructs a new MessageFormat from an existing one.
* @stable ICU 2.0
*/
MessageFormat(const MessageFormat&);
/**
* Assignment operator.
* @stable ICU 2.0
*/
const MessageFormat& operator=(const MessageFormat&);
/**
* Destructor.
* @stable ICU 2.0
*/
virtual ~MessageFormat();
/**
* Clones this Format object polymorphically. The caller owns the
* result and should delete it when done.
* @stable ICU 2.0
*/
virtual Format* clone(void) const;
/**
* Returns true if the given Format objects are semantically equal.
* Objects of different subclasses are considered unequal.
* @param other the object to be compared with.
* @return true if the given Format objects are semantically equal.
* @stable ICU 2.0
*/
virtual UBool operator==(const Format& other) const;
/**
* Sets the locale. This locale is used for fetching default number or date
* format information.
* @param theLocale the new locale value to be set.
* @stable ICU 2.0
*/
virtual void setLocale(const Locale& theLocale);
/**
* Gets the locale. This locale is used for fetching default number or date
* format information.
* @return the locale of the object.
* @stable ICU 2.0
*/
virtual const Locale& getLocale(void) const;
/**
* Applies the given pattern string to this message format.
*
* @param pattern The pattern to be applied.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @stable ICU 2.0
*/
virtual void applyPattern(const UnicodeString& pattern,
UErrorCode& status);
/**
* Applies the given pattern string to this message format.
*
* @param pattern The pattern to be applied.
* @param parseError Struct to recieve information on position
* of error within pattern.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @stable ICU 2.0
*/
virtual void applyPattern(const UnicodeString& pattern,
UParseError& parseError,
UErrorCode& status);
/**
* Returns a pattern that can be used to recreate this object.
*
* @param appendTo Output parameter to receive the pattern.
* Result is appended to existing contents.
* @return Reference to 'appendTo' parameter.
* @stable ICU 2.0
*/
virtual UnicodeString& toPattern(UnicodeString& appendTo) const;
/**
* Sets subformats.
* See the class description about format numbering.
* The caller should not delete the Format objects after this call.
* The array formatsToAdopt is not itself adopted. Its
* ownership is retained by the caller. If the call fails because
* memory cannot be allocated, then the formats will be deleted
* by this method, and this object will remain unchanged.
*
* @stable ICU 2.0
* @param formatsToAdopt the format to be adopted.
* @param count the size of the array.
*/
virtual void adoptFormats(Format** formatsToAdopt, int32_t count);
/**
* Sets subformats.
* See the class description about format numbering.
* Each item in the array is cloned into the internal array.
* If the call fails because memory cannot be allocated, then this
* object will remain unchanged.
*
* @stable ICU 2.0
* @param newFormats the new format to be set.
* @param cnt the size of the array.
*/
virtual void setFormats(const Format** newFormats,int32_t cnt);
/**
* Sets one subformat.
* See the class description about format numbering.
* The caller should not delete the Format object after this call.
* If the number is over the number of formats already set,
* the item will be deleted and ignored.
* @stable ICU 2.0
* @param formatNumber index of the subformat.
* @param formatToAdopt the format to be adopted.
*/
virtual void adoptFormat(int32_t formatNumber, Format* formatToAdopt);
/**
* Sets one subformat.
* See the class description about format numbering.
* If the number is over the number of formats already set,
* the item will be ignored.
* @param formatNumber index of the subformat.
* @param format the format to be set.
* @stable ICU 2.0
*/
virtual void setFormat(int32_t formatNumber, const Format& format);
/**
* Gets an array of subformats of this object. The returned array
* should not be deleted by the caller, nor should the pointers
* within the array. The array and its contents remain valid only
* until the next call to any method of this class is made with
* this object. See the class description about format numbering.
* @param count output parameter to receive the size of the array
* @return an array of count Format* objects, or NULL if out of
* memory. Any or all of the array elements may be NULL.
* @stable ICU 2.0
*/
virtual const Format** getFormats(int32_t& count) const;
/**
* Formats the given array of arguments into a user-readable string.
* Does not take ownership of the Formattable* array or its contents.
*
* @param source An array of objects to be formatted.
* @param count The number of elements of 'source'.
* @param appendTo Output parameter to receive result.
* Result is appended to existing contents.
* @param ignore Not used; inherited from base class API.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @return Reference to 'appendTo' parameter.
* @stable ICU 2.0
*/
UnicodeString& format( const Formattable* source,
int32_t count,
UnicodeString& appendTo,
FieldPosition& ignore,
UErrorCode& status) const;
/**
* Formats the given array of arguments into a user-readable string
* using the given pattern.
*
* @param pattern The pattern.
* @param arguments An array of objects to be formatted.
* @param count The number of elements of 'source'.
* @param appendTo Output parameter to receive result.
* Result is appended to existing contents.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @return Reference to 'appendTo' parameter.
* @stable ICU 2.0
*/
static UnicodeString& format( const UnicodeString& pattern,
const Formattable* arguments,
int32_t count,
UnicodeString& appendTo,
UErrorCode& status);
/**
* Formats the given array of arguments into a user-readable
* string. The array must be stored within a single Formattable
* object of type kArray. If the Formattable object type is not of
* type kArray, then returns a failing UErrorCode.
*
* @param obj A Formattable of type kArray containing
* arguments to be formatted.
* @param appendTo Output parameter to receive result.
* Result is appended to existing contents.
* @param pos On input: an alignment field, if desired.
* On output: the offsets of the alignment field.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @return Reference to 'appendTo' parameter.
* @stable ICU 2.0
*/
virtual UnicodeString& format(const Formattable& obj,
UnicodeString& appendTo,
FieldPosition& pos,
UErrorCode& status) const;
/**
* Formats the given array of arguments into a user-readable
* string. The array must be stored within a single Formattable
* object of type kArray. If the Formattable object type is not of
* type kArray, then returns a failing UErrorCode.
*
* @param obj The object to format
* @param appendTo Output parameter to receive result.
* Result is appended to existing contents.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @return Reference to 'appendTo' parameter.
* @stable ICU 2.0
*/
UnicodeString& format(const Formattable& obj,
UnicodeString& appendTo,
UErrorCode& status) const;
/**
* Parses the given string into an array of output arguments.
*
* @param source String to be parsed.
* @param pos On input, starting position for parse. On output,
* final position after parse. Unchanged if parse
* fails.
* @param count Output parameter to receive the number of arguments
* parsed.
* @return an array of parsed arguments. The caller owns both
* the array and its contents.
* @stable ICU 2.0
*/
virtual Formattable* parse( const UnicodeString& source,
ParsePosition& pos,
int32_t& count) const;
/**
* Parses the given string into an array of output arguments.
*
* @param source String to be parsed.
* @param count Output param to receive size of returned array.
* @param status Input/output error code. If the
* pattern cannot be parsed, set to failure code.
* @return an array of parsed arguments. The caller owns both
* the array and its contents.
* @stable ICU 2.0
*/
virtual Formattable* parse( const UnicodeString& source,
int32_t& count,
UErrorCode& status) const;
/**
* Parses the given string into an array of output arguments
* stored within a single Formattable of type kArray.
*
* @param source The string to be parsed into an object.
* @param result Formattable to be set to the parse result.
* If parse fails, return contents are undefined.
* @param pos On input, starting position for parse. On output,
* final position after parse. Unchanged if parse
* fails.
* @stable ICU 2.0
*/
virtual void parseObject(const UnicodeString& source,
Formattable& result,
ParsePosition& pos) const;
/**
* 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.
*
* @return 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 ICU 2.0
*/
virtual UClassID getDynamicClassID(void) const;
/**
* 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()) ...
*
* @return The class ID for all objects of this class.
* @stable ICU 2.0
*/
static UClassID getStaticClassID(void);
private:
Locale fLocale;
UnicodeString fPattern;
Format** formatAliases; // see getFormats
int32_t formatAliasesCapacity;
MessageFormat(); // default constructor not implemented
/**
* A structure representing one subformat of this MessageFormat.
* Each subformat has a Format object, an offset into the plain
* pattern text fPattern, and an argument number. The argument
* number corresponds to the array of arguments to be formatted.
* @internal
*/
class Subformat {
public:
/**
* @internal
*/
Format* format; // formatter
/**
* @internal
*/
int32_t offset; // offset into fPattern
/**
* @internal
*/
int32_t arg; // 0-based argument number
/**
* Clone that.format and assign it to this.format
* Do NOT delete this.format
* @internal
*/
Subformat& operator=(const Subformat& that) {
format = that.format ? that.format->clone() : NULL;
offset = that.offset;
arg = that.arg;
return *this;
}
/**
* @internal
*/
UBool operator==(const Subformat& that) const {
// Do cheap comparisons first
return offset == that.offset &&
arg == that.arg &&
((format == that.format) || // handles NULL
(*format == *that.format));
}
/**
* @internal
*/
UBool operator!=(const Subformat& that) const {
return !operator==(that);
}
};
/**
* A MessageFormat contains an array of subformats. This array
* needs to grow dynamically if the MessageFormat is modified.
*/
Subformat* subformats;
int32_t subformatCount;
int32_t subformatCapacity;
/**
* A MessageFormat formats an array of arguments. Each argument
* has an expected type, based on the pattern. For example, if
* the pattern contains the subformat "{3,number,integer}", then
* we expect argument 3 to have type Formattable::kLong. This
* array needs to grow dynamically if the MessageFormat is
* modified.
*/
Formattable::Type* argTypes;
int32_t argTypeCount;
int32_t argTypeCapacity;
// Variable-size array management
UBool allocateSubformats(int32_t capacity);
UBool allocateArgTypes(int32_t capacity);
/**
* Default Format objects used when no format is specified and a
* numeric or date argument is formatted. These are volatile
* cache objects maintained only for performance. They do not
* participate in operator=(), copy constructor(), nor
* operator==().
*/
NumberFormat* defaultNumberFormat;
DateFormat* defaultDateFormat;
/**
* Method to retrieve default formats (or NULL on failure).
* These are semantically const, but may modify *this.
*/
const NumberFormat* getDefaultNumberFormat(UErrorCode&) const;
const DateFormat* getDefaultDateFormat(UErrorCode&) const;
/**
* Finds the word s, in the keyword list and returns the located index.
* @param s the keyword to be searched for.
* @param list the list of keywords to be searched with.
* @return the index of the list which matches the keyword s.
*/
static int32_t findKeyword( const UnicodeString& s,
const UChar * const *list);
/**
* Formats the array of arguments and copies the result into the
* result buffer, updates the field position.
*
* @param arguments The formattable objects array.
* @param cnt The array count.
* @param appendTo Output parameter to receive result.
* Result is appended to existing contents.
* @param status Field position status.
* @param recursionProtection
* Initially zero. Bits 0..9 are used to indicate
* that a parameter has already been seen, to
* avoid recursion. Currently unused.
* @param success The error code status.
* @return Reference to 'appendTo' parameter.
*/
UnicodeString& format( const Formattable* arguments,
int32_t cnt,
UnicodeString& appendTo,
FieldPosition& status,
int32_t recursionProtection,
UErrorCode& success) const;
void makeFormat(int32_t offsetNumber,
UnicodeString* segments,
UParseError& parseError,
UErrorCode& success);
/**
* Convenience method that ought to be in NumberFormat
*/
NumberFormat* createIntegerFormat(const Locale& locale, UErrorCode& status) const;
/**
* Checks the range of the source text to quote the special
* characters, { and ' and copy to target buffer.
* @param source
* @param start the text offset to start the process of in the source string
* @param end the text offset to end the process of in the source string
* @param appendTo Output parameter to receive result.
* Result is appended to existing contents.
*/
static void copyAndFixQuotes(const UnicodeString& appendTo, int32_t start, int32_t end, UnicodeString& target);
/**
* Returns array of argument types in the parsed pattern
* for use in C API. Only for the use of umsg_vformat(). Not
* for public consumption.
* @param listCount Output parameter to receive the size of array
* @return The array of formattable types in the pattern
* @internal
*/
const Formattable::Type* getArgTypeList(int32_t& listCount) const {
listCount = argTypeCount;
return argTypes;
}
friend class MessageFormatAdapter; // getFormatTypeList() access
};
inline UnicodeString&
MessageFormat::format(const Formattable& obj,
UnicodeString& appendTo,
UErrorCode& status) const {
return Format::format(obj, appendTo, status);
}
U_NAMESPACE_END
#endif /* #if !UCONFIG_NO_FORMATTING */
#endif // _MSGFMT
//eof