* Many of the concrete subclasses of Format employ the notion of * a pattern. A pattern is a string representation of the rules which * govern the interconversion between values and strings. For example, * a DecimalFormat object may be associated with the pattern * "$#,##0.00;($#,##0.00)", which is a common US English format for * currency values, yielding strings such as "$1,234.45" for 1234.45, * and "($987.65)" for 987.6543. The specific syntax of a pattern * is defined by each subclass. *
* Even though many subclasses use patterns, the notion of a pattern * is not inherent to Format classes in general, and is not part of * the explicit base class protocol. *
* Two complex formatting classes bear mentioning. These are * MessageFormat and ChoiceFormat. ChoiceFormat is a subclass of * NumberFormat which allows the user to format different number ranges * as strings. For instance, 0 may be represented as "no files", 1 as * "one file", and any number greater than 1 as "many files". * MessageFormat is a formatter which utilizes other Format objects to * format a string containing with multiple values. For instance, * A MessageFormat object might produce the string "There are no files * on the disk MyDisk on February 27, 1997." given the arguments 0, * "MyDisk", and the date value of 2/27/97. See the ChoiceFormat * and MessageFormat headers for further information. *
* If formatting is unsuccessful, a failing UErrorCode is returned when * the Format cannot format the type of object, otherwise if there is * something illformed about the the Unicode replacement character * 0xFFFD is returned. *
* If there is no match when parsing, a parse failure UErrorCode is * retured for methods which take no ParsePosition. For the method * that takes a ParsePosition, the index parameter is left unchanged. *
* [Subclassing.] All base classes that provide static functions that * create objects for Locales must implement the following static: *
* . public static const Locale* getAvailableLocales(long&) **/ class U_I18N_API Format { public: virtual ~Format(); /** * Return true if the given Format objects are semantically equal. * Objects of different subclasses are considered unequal. * @stable */ virtual UBool operator==(const Format& other) const = 0; /** * Return true if the given Format objects are not semantically * equal. * @stable */ UBool operator!=(const Format& other) const { return !operator==(other); } /** * Clone this object polymorphically. The caller is responsible * for deleting the result when done. * @stable */ virtual Format* clone() const = 0; /** * Formats an object to produce a string. * * @param obj The object to format. * @param result Output parameter which will be filled in with the * formatted string. * @param status Output parameter filled in with success or failure status. * @return Reference to 'result' parameter. * @stable */ UnicodeString& format(const Formattable& obj, UnicodeString& result, UErrorCode& status) const; /** * 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. * * @param obj The object to format. * @param toAppendTo Where the text is to be appended. * @param pos On input: an alignment field, if desired. * On output: the offsets of the alignment field. * @param status Output param filled with success/failure status. * @return The value passed in as toAppendTo (this allows chaining, * as with UnicodeString::append()) * @stable */ virtual UnicodeString& format(const Formattable& obj, UnicodeString& toAppendTo, FieldPosition& pos, UErrorCode& status) const = 0; /** * Parse a string to produce an object. This is a pure virtual * method which subclasses must implement. This method allows * polymorphic parsing of strings into Formattable objects. *
* 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. *
* Example: *
* Parsing "_12_xy" (where _ represents a space) for a number, * with index == 0 will result in the number 12, with * parse_pos.index updated to 3 (just before the second space). * Parsing a second time will result in a failing UErrorCode since * "xy" is not a number, and leave index at 3. *
* Subclasses will typically supply specific parse methods that * return different types of values. Since methods can't overload * on return types, these will typically be named "parse", while * this polymorphic method will always be called parseObject. Any * parse method that does not take a parse_pos should set status * to an error value when no text in the required format is at the * start position. * * @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 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 */ virtual void parseObject(const UnicodeString& source, Formattable& result, ParsePosition& parse_pos) const = 0; /** * Parses a string to produce an object. This is a convenience method * which calls the pure virtual parseObject() method, and returns a * failure UErrorCode if the ParsePosition indicates failure. * * @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 status Output param to be filled with success/failure * result code. * @stable */ void parseObject(const UnicodeString& source, Formattable& result, UErrorCode& status) const; /** * Returns a unique class ID POLYMORPHICALLY. Pure virtual method. * 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. *
* Concrete subclasses of Format must implement getDynamicClassID() * and also a static method and data member: * * static UClassID getStaticClassID() { return (UClassID)&fgClassID; } * static char fgClassID; * * @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 */ virtual UClassID getDynamicClassID() const = 0; protected: /** * Default constructor for subclass use only. Does nothing. * @stable */ Format(); /** * @stable */ Format(const Format&); // Does nothing; for subclasses only /** * @stable */ Format& operator=(const Format&); // Does nothing; for subclasses }; #endif // _FORMAT //eof