Date::Manip::Objects(3User Contributed Perl DocumentatiDate::Manip::Objects(3)NAMEDate::Manip::Objects - A description of the various Date::Manip objects
SYNOPSIS
The Date::Manip package consist of several modules, each of which
perform a set of operations on a specific type of information. This
document describes how the various modules work together.
DESCRIPTION
Date::Manip consists of several different modules, each of which deal
with a different type of data.
The primary modules are:
Date::Manip::Obj
The Date::Manip::Obj module is not intended for direct use. It is
used as a base class for all other Date::Manip classes described
below.
The Date::Manip::Obj module contains some functions which are
inherited by all these classes, so to understand all of the methods
available to any of the classes below, you must include those
documented in the Date::Manip::Obj class.
Date::Manip::Base
The Date::Manip::Base is used to perform basic operations including
basic date operations, management of configuration options,
handling the definitions used in different languages, etc.
A Date::Manip::Base object does not, of itself, contain any date
information. Instead, it contains configuration information which
determines how the Date::Manip package performs date operations.
The configuration information is documented in the
Date::Manip::Config manual.
The Date::Manip::Base object has one other property that is very
important. When performing basic date properties, some intermediate
results are cached in the object which leads to significant
performance increases in later operations. As such, it is important
to reuse the object as much as possible, rather than creating new
Date::Manip::Base objects all the time.
Much of the information in this document is related to this issue,
and tells how to create various objects in order to get the most
efficient reuse of this cached data.
Because all other objects depend on a Date::Manip::Base object, a
Date::Manip::Base object is embedded in all other objects, and the
same Base object can be embedded as often as desired to achieve
maximum performance.
Date::Manip::TZ
The Date::Manip::TZ module adds support for time zones. It is used
to verify date and time zone information, convert dates from one
time zone to another, and handle all daylight saving time
transitions.
All higher level objects (those listed next) depend on both a
Date::Manip::Base and Date::Manip::TZ object, so one of each are
embedded into those objects.
Date::Manip::Date
Date::Manip::Delta
Date::Manip::Recur
These are the primary modules which are used to perform all high
level date operations.
The Date::Manip::Date class performs operations on dates (which
includes a date, time, and time zone). The Date::Manip::Delta class
performs operations with deltas (amounts of time). The
Date::Manip::Recur class performs operations on recurring events.
As mentioned above, each of these high level classes rely on both a
Date::Manip::TZ object and a Date::Manip::Base object, and one of
each is embedded in each object.
A Date::Manip::Date object contains a single date, so in order to
work with multiple dates, multiple Date::Manip::Date objects will
need to be created. In order to make the most effective use of
cached information in the Date::Manip::Base object, the same
Date::Manip::Base object can be embedded in each of the higher
level objects.
The same goes for multiple Date::Manip::Delta and
Date::Manip::Recur objects.
WORKING WITH DATE::MANIP OBJECTS
The basic way to create the first instance of a Date::Manip object (of
any class) is to use the "new" method of the appropriate class. This
is documented in the Date::Manip::Obj manual. For example:
$tz = new Date::Manip::TZ;
$date = new Date::Manip::Date;
Optionally, config options can be passed in:
$tz = new Date::Manip::TZ \@opts;
$date = new Date::Manip::Date \@opt;
In order to create additional Date::Manip objects, a previously created
object should be passed in as the first argument. This will allow the
same Base object to be embedded in both in order to maximize data reuse
of the cached intermediate results, and will result in much better
performance. For example:
$date1 = new Date::Manip::Date;
$date2 = new Date::Manip::Date $date1;
As a general rule, you should only pass in configuration options when
the first object is created. In other words, the following behavior:
$date1 = new Date::Manip::Date [$opt1,$val1,$opt2,$val2];
$date2 = new Date::Manip::Date $date1;
will behave differently than:
$date1 = new Date::Manip::Date [$opt1,$val1];
$date2 = new Date::Manip::Date $date1,[$opt2,$val2];
In the first case, only a single Date::Manip::Base object is created.
In the second case, two Date::Manip::Base objects are created.
Unless you specifically need to work with multiple sets of
configurations (which is described below), it is far less complicated,
and results in better performance, to work with only a single
Date::Manip::Base object.
It is also preferred that all configuration be done soon after the
first object is created in order to keep things clear.
To following example illustrates a potential pitfall:
$date1 = new Date::Manip::Date [$opt1,$val1];
$date2 = new Date::Manip::Date $date1,
$date1->config($opt2,$val2);
The first two lines create a total of 4 Date::Manip object. The first
line creates a Date::Manip::Base object and a Date::Manip::TZ object,
and then a Date::Manip::Date object with the first two embedded in it.
The second line creates a second Date::Manip::Date object, with the
same Date::Manip::Base and Date::Manip::TZ objects embedded in it.
The third line alters the configuration information used by the $date1
object. Since configuration information is stored only in the Base
object, that object is modified, and therefore, the configuration
change impacts both $date1 and $date2 objects (and any additional
Date::Manip objects created from either of them).
In order to keep things clean, it is highly recommended that the above
example be reordered:
$date1 = new Date::Manip::Date [$opt1,$val1];
$date1->config($opt2,$val2);
$date2 = new Date::Manip::Date $date1,
and all configuration changes be made immediately after (or as close to
it as possible) the creation of the first object.
MULTIPLE CONFIGURATIONS
Occasionally, it may be useful to have multiple sets of configurations.
In order to do this, multiple Date::Manip::Base objects must be created
(each with their own set of configuration options), and then new
Date::Manip objects are created with the appropriate Date::Manip::Base
object embedded in them.
Possible reasons include:
Parsing multiple languages
A Date::Manip::Base object includes information about a single
language. If you need to parse dates from two (or more) languages,
a Date::Manip::Base object needs to be created for each one. This
could be done as:
$date_eng1 = new Date::Manip::Date ["language","English"];
$date_spa1 = new Date::Manip::Date $date_eng1,["language","Spanish"];
Any additional Date::Manip objects created from the first will work
with English. Additional objects created from the second will work
in Spanish.
Business modes for different countries and/or businesses
If you are doing business mode calculations (see Date::Manip::Calc)
for two different businesses which have different holiday lists,
work weeks, or business days, you can create different objects
which read different config files (see Date::Manip::Config) with
the appropriate description of each.
The primary issue when dealing with multiple configurations is that it
is necessary for the programmer to manually keep track of which
Date::Manip objects work with each configuration. For example, refer to
the following lines:
$date1 = new Date::Manip::Date [$opt1,$val1];
$date2 = new Date::Manip::Date $date1, [$opt2,$val2];
$date3 = new Date::Manip::Date $date1;
$date4 = new Date::Manip::Date $date2;
The first line creates 3 objects (a Date::Manip::Base object, a
Date::Manip::TZ object, and a Date::Manip::Date object). The
Date::Manip::Base object has the configuration set to contain the
value(s) passed in as the final list reference argument.
The second line creates 3 new objects (a second Date::Manip::Base
object, a second Date::Manip::TZ object, and a second Date::Manip::Date
object). Since a list reference containing config variables is passed
in, a new Date::Manip::Base object is created, rather than reusing the
first one. The second Date::Manip::Base object contains all the config
from the first, as well as the config variables passed in in the list
reference argument.
The third line creates another Date::Manip::Date object which uses the
first Date::Manip::Base and Date::Manip::TZ objects embedded in it.
The fourth line creates another Date::Manip::Date object which uses the
second Date::Manip::Base and Date::Manip::TZ objects embedded in it.
Luckily, most of the time there will only be one set of configuration
options used, so this complexity is really for a very special, and not
widely used, bit of functionality.
WORKING WITH BOTH HIGH LEVEL AND LOWER LEVEL OBJECTS
If you are working with any higher level Date::Manip modules
(Date::Manip::Date, Date::Manip::Delta, or Date::Manip::Recur), you
probably will not need to work with the lower Date::Manip::Base and
Date::Manip::TZ objects directly. However, if you want to make use of
some of the faster Date::Manip::Base operations, or work directly with
time zones, you can access the lower level objects using the "base" and
"tz" methods from the higher level object.
More information is in the Date::Manip::Obj manual.
BUGS AND QUESTIONS
Please refer to the Date::Manip::Problems documentation for information
on submitting bug reports or questions to the author.
SEE ALSO
Date::Manip - main module documentation
LICENSE
This script is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
AUTHOR
Sullivan Beck (sbeck@cpan.org)
perl v5.10.1 2010-01-12 Date::Manip::Objects(3)
