DB Interface Module User’s Guide : PART II Using the Basic Features : Chapter 7 The Data Model : The Value Layer : RWCString
RWCString
Class RWCString can be found in the Essential Tools Module. It is an industry standard for string manipulation, providing string processing features that are just as efficient as those in C, but far less prone to errors. Its features include memory management, collation, substrings, pattern matching, regular expressions, I/O, tokenizing, and support for multibyte strings.
Class RWCString has member functions to read, compare, store, restore, concatenate, prefix, and append RWCStrings and char*'s. Operators allow access to individual characters, with or without bounds checking.
For a full discussion of the features of this class, please see the Essential Tools Module User's Guide and the SourcePro API Reference Guide.
RWDateTime
Class RWDateTime, also contained in the Essential Tools Module, is the primary class used for dates and times in the DB Interface Module. This class serves as a compact representation for calendar calculations. It shields you from many of the details of programming with time elements, like leap years, and performs conversions to and from conventional calendar formats.
SourcePro DB compatibility is provided to RWDateTime instances that are initialized to either RWDateTime::null or a valid date. For a full discussion of the many features of this class, please see the Essential Tools Module User's Guide and the SourcePro API Reference Guide.
When RWDateTime is used to either write or extract data to or from a database, by default it uses the local time zone represented by RWZone::local(). Methods on RWDBDatabase and RWDBConnection allow you to specify a different time zone.
 
const RWZone* RWDBDatabase::timeZone(const RWZone* zone)
const RWZone& RWDBDatabase::timeZone() const
The first method sets the time zone on the RWDBDatabase instance, and all RWDBConnection instances produced by it after the time zone is set. The RWDBDatabase instance retains a reference to the time zone, hence it is the application's responsibility to ensure that the time zone has a lifetime greater than the RWDBDatabase instance or any object produced from it. The second method allows you to determine the current setting for this RWDBDatabase.
 
const RWZone* RWDBConnection::timeZone(const RWZone* zone)
const RWZone& RWDBConnection::timeZone() const
The first method sets the time zone for the specific RWDBConnection instance. The RWDBConnection instance retains a reference to the time zone, hence it is the application's responsibility to ensure that the time zone has a lifetime greater than the RWDBConnection instance or any object using it. The second method allows you to determine the current setting for this RWDBConnection.
NOTE >> If the database client you are using provides a time zone setting on its connections, the above methods do not set or get those time zone settings. If you wish to get or set the time zone setting on the database client connection, you can do so by executing the database-specific SQL for getting or setting the time zone using RWDBConnection::executeSql().
Example
The following example shows how RWDateTime performs date calculations. This code prints out the date January 6, 1990, then calculates and prints the date of the previous Sunday, using the global locale:
 
#include <rw/db/db.h>
#include <rw/rstream.h>
 
int
main() {
RWDateTime dd(1990U, 1, 6);
 
cout << dd.asString() << ", a " << dd.weekDayName() << endl;
 
RWDateTime prev = dd.previous("Sunday");
 
cout << "The previous Sunday is: " << prev.asString() << endl;
return 0;
}
Program output:
01/06/90 00:00:00.000, a Saturday
The previous Sunday is: 12/31/89 00:00:00.000
Constructors
An RWDateTime may be constructed in many ways. For example, you can:
• Construct an RWDateTime with the current date:
 
RWDateTime dt(RWDateTime::setCurrentTime);
• Construct an RWDateTime for a given year, month, and day:
 
RWDateTime d1(1924U, 1, 24); // Jan.24, 1924
• Construct an RWDateTime from an RWDate, supplying hours, minutes, seconds, and milliseconds:
 
RWDate d(10, 3, 90); // Mar. 10, 1990
RWDateTime dt(d, 1, 30, 30, 100) // Mar. 10, 1990 1:30:30.100
 
In the first example, we use the enumerated constructor to construct RWDateTime with current value. If you are constructing an array and must fill in today’s date, you must assign the dates explicitly (see the Essential Tools documentation for more details).
There are many other constructors, including those that use RWDate or RWTime in various ways. There are accessors for each component of an RWDateTime (years, months, days, hours, and so on). RWDateTime provides powerful localization features which may be accessed and changed via the RWDateTime interface. Member operators and functions allow a complete range of arithmetic manipulations on date and time values.
Complete information on the capabilities of RWDateTime can be found in the Essential Tools Module User's Guide and the SourcePro API Reference Guide.
RWTimeTuple and RWTimeTupleOffset
Essential Tools Module classes RWTimeTuple and RWTimeTupleOffset also represent dates and times and can be used as an alternative to RWDateTime in some circumstances. These classes store a tuple of each calendar component of a date and time. If you need picosecond precision or don’t need to perform calculations and comparisons of dates, these classes may offer better performance. For more information, see “Date and Time Classes” in the Essential Tools Module User's Guide.