# Copyright (c) 2008-2021 Sullivan Beck. All rights reserved.
# This program is free software; you can redistribute it and/or modify it
# under the same terms as Perl itself.

=pod

=head1 NAME

Date::Manip::Obj - Base class for Date::Manip objects

=head1 SYNOPSIS

The Date::Manip::Obj class is the base class used for the following
Date::Manip classes:

=over 4

=item L<Date::Manip::Base>

=item L<Date::Manip::TZ>

=item L<Date::Manip::Date>

=item L<Date::Manip::Delta>

=item L<Date::Manip::Recur>

=back

This module is not intended to be called directly and performs no
useful function by itself. Instead, use the various derived classes
which inherit from it.

=head1 DESCRIPTION

This module contains a set of methods used by all Date::Manip classes
listed above.

You should be familiar with the L<Date::Manip::Objects> and
L<Date::Manip::Config> documentation.

In the method descriptions below, L<Date::Manip::Date> objects will
usually be used as examples, but (unless otherwise stated), all of the
classes listed above have the same methods, and work in the same
fashion.

=head1 METHODS FOR CREATING OBJECTS

In the examples below, any variable named some variation of C<$date> (C<$date>,
C<$date1>, C<$date2>, ...) is a L<Date::Manip::Date> object. Similarly, C<$delta>,
C<$recur>, C<$tz>, and C<$base> refer to objects in the appropriate class.

Any C<$obj> variable refers to an object in any of the classes.

=over 4

=item B<new>

There are two ways to use the new method. They are:

   $obj2  = new CLASS ($obj1,$string,@parse_opts,\@opts);
   $obj2  = $obj1->new($string,@parse_opts,\@opts)

In both cases, all arguments are optional.

Both methods are used to create a new object of a given class.  In the
first case, B<CLASS> is the class of the new object. For example:

   $date  = new Date::Manip::Date;
   $delta = new Date::Manip::Delta;

In the second method, the class of the new object will be derived from
the first object.  For example:

   $date1 = new Date::Manip::Date;
   $date2 = $date1->new();

the class of the second object (C<$date2>) is L<Date::Manip::Date>
because that is the class of the object (C<$date1>) used to create it.

In both first method (when a C<$obj1> is passed in) and always in the
second method, the new object will share as much information from the
old object (C<$obj1>) as possible.

For example, if you call either of these:

   $date2 = new Date::Manip::Date $date1;
   $date2 = $date1->new();

the new date object will use the same embedded L<Date::Manip::TZ> and
L<Date::Manip::Base> objects.

When specifying CLASS and including an old object, objects do not need to
be of the same class.  For example, the following are all valid:

   $date = new Date::Manip::Date $delta;
   $date = new Date::Manip::Date $tz;

You can even do:

   $date = new Date::Manip::Date $base;

but this will have to create a completely new L<Date::Manip::TZ> object,
which means that optimal performance may not be achieved if a
L<Date::Manip::TZ> object already exists.

There are two special cases. Either of the following will create
a new L<Date::Manip::Base> object for handling multiple configurations:

   $base2 = new Date::Manip::Base $base1;
   $base2 = $base1->new();

Either of the following will create a new L<Date::Manip::TZ> object with
the same L<Date::Manip::Base> object embedded in it:

   $tz2   = new Date::Manip::TZ $tz1;
   $tz2   = $tz1->new();

The new base object will initially have the same configuration as the
original base object, but changing it's configuration will not
affect the original base object.

If the C<\@opts> argument is passed in, it is a list reference containing
a list suitable for passing to the B<config> method (described below). In
this case, a new L<Date::Manip::Base> object (and perhaps L<Date::Manip::TZ>
object) will be created. The new Base object will start as identical
to the original one (if a previously defined object was used to create
the new object) with the additional options in C<@opts> added.

In other words, the following are equivalent:

   $date  = new Date::Manip::Date $obj,\@opts;

   $base  = $obj->base();
   $base2 = $base->new();
   $date = new Date::Manip::Date $base2;
   $date->config(@opts);

It should be noted that the options are applied to the NEW L<Date::Manip::Base>
object, not the old one.

An optional string (C<$string> and parse opts C<@parse_opts>) may be
passed in only when creating a L<Date::Manip::Date>,
L<Date::Manip::Delta>, or L<Date::Manip::Recur> object.  If passed in
when creating a L<Date::Manip::TZ> or L<Date::Manip::Base> object, a
warning will be issued, but execution will continue.

If the string is included, it will be parsed to give an initial value
to the object. This will only be done AFTER any options are handled,
so the following are equivalent:

   $date = new Date::Manip::Date $string,@parse_opts,\@opts;

   $date = new Date::Manip::Date;
   $date->config(@opts);
   $date->parse($string,@parse_opts);

Once a L<Date::Manip::Date> object (or any object in any other
Date::Manip class) is created, it should always be used to create
additional objects in order to preserve cached data for optimal
performance and memory usage.

The one caveat is if you are working with multiple configurations
as described in the L<Date::Manip::Objects> document. In that case,
you may need to create completely new objects to allow multiple
L<Date::Manip::Base> objects to be used.

=item B<new_config>

   $obj2 = $obj1->new_config($string,\@opts);

This creates a new instance with a new L<Date::Manip::Base> object (and possibly
a new L<Date::Manip::TZ> object).

For example,

   $date2 = $date1->new_config();

creates a new L<Date::Manip::Date> object with a new L<Date::Manip::TZ> (and
L<Date::Manip::Base>) object. Initially, it is the same configuration as
the original object.

If the object is a L<Date::Manip::Base> object, the following are equivalent:

   $base2 = $base1->new_config();

   $base2 = $base1->new();

Both C<$string> and C<\@opts> are optional. They are used in the same way they
are used in the new method.

=item B<new_date>

=item B<new_delta>

=item B<new_recur>

These are shortcuts for specifying the class. The following sets of
calls are all equivalent:

   $date  = $obj->new_date();
   $date  = new Date::Manip::Date($obj);

   $delta = $obj->new_delta();
   $delta = new Date::Manip::Date($obj);

These methods all allow optional C<($string,\@opts)> arguments.

=back

=head1 OTHER METHODS

=over 4

=item B<base>

=item B<tz>

   $base = $obj->base();

This returns the L<Date::Manip::Base> object associated with the
given object.

If C<$obj> is a L<Date::Manip::Base> object, nothing is returned (i.e. it doesn't
create a new copy of the object).

   $tz = $obj->tz();

This returns the L<Date::Manip::TZ> object associated with the
given object. If C<$obj> is a L<Date::Manip::TZ> or L<Date::Manip::Base> object,
nothing is returned.

=item B<config>

   $obj->config($var1,$val1,$var2,$val2,...);

This will set the value of any configuration variables. Please refer to the
L<Date::Manip::Config> manual for a list of all configuration variables and their
description.

=item B<get_config>

   @var = $obj->get_config();
   $val = $obj->get_config($var1);
   @val = $obj->get_config($var1,$var2,...);

This queries the current config values.  With no argument, it will return
the list of config variables (all lowercase).

With one or more arguments, it returns the current values for the config
variables passed in (case insensitive).

=item B<err>

   $err = $obj->err();

This will return the full error message if the previous operation failed
for any reason.

   $obj->err(1);

will clear the error code.

=item B<is_date>

=item B<is_delta>

=item B<is_recur>

   $flag = $obj->is_date();

Returns 0 or 1, depending on the object. For example, a L<Date::Manip::Date>
object returns 1 with the is_date method, and 0 for the other two.

=item B<version>

   $vers = $obj->version($flag);

This returns the version of Date::Manip.

If C<$flag> is passed in, and C<$obj> is not a L<Date::Manip::Base> object, the
version and timezone information will be passed back.

=back

=head1 KNOWN BUGS

None known.

=head1 BUGS AND QUESTIONS

Please refer to the L<Date::Manip::Problems> documentation for
information on submitting bug reports or questions to the author.

=head1 SEE ALSO

L<Date::Manip>        - main module documentation

=head1 LICENSE

This script is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=head1 AUTHOR

Sullivan Beck (sbeck@cpan.org)

=cut