Provided by: libclass-std-utils-perl_0.0.3-2_all bug

NAME

       Class::Std::Utils - Utility subroutines for building "inside-out" objects

VERSION

       This document describes Class::Std::Utils version 0.0.3

SYNOPSIS

           use Class::Std::Utils;

           # Constructor for anonymous scalars...
           my $new_object = bless anon_scalar(), $class;

           # Convert an object reference into a unique ID number...
           my $ID_num = ident $new_object;

           # Extract class-specific arguments from a hash reference...
           my %args = extract_initializers_from($arg_ref);

DESCRIPTION

       This module provides three utility subroutines that simplify the creation of "inside-out" classes. See
       Chapters 15 and 16 of "Perl Best Practices" (O'Reilly, 2005) for details.

INTERFACE

       "anon_scalar()"
           This subroutine is always exported. It takes no arguments and returns a reference to an anonymous
           scalar, suitable for blessing as an object.

       "ident()"
           This subroutine is always exported. It takes one argument--a reference-- and acts exactly like the
           "Scalar::Util::refaddr()", returning a unique integer value suitable for identifying the referent.

       "extract_initializers_from()"
           This subroutine is always exported. It takes one argument--a hash reference-- and returns a
           "flattened" set of key/value pairs extracted from that hash.

           The typical usage is:

               my %class_specific_args = extract_initializers_from($args_ref);

           The argument hash is flattened as described in Chapter 16 of "Perl Best Practices":

               The subroutine is always called with the original multi-level argument hash from the constructor.
               It then looks up the class's own name (i.e.  its "caller" package) in the argument hash, to see
               if an initializer with that key has been defined. Finally, "extract_initializers_for()" returns
               the flattened set of key/value pairs for the class's initializer set, by appending the class-
               specific initializer subhash to the end of the original generic initializer hash. Appending the
               specific initializers after the generic ones means that any key in the class- specific set will
               override any key in the generic set, thereby ensuring that the most relevant initializers are
               always selected, but that generic initializers are still available where no class-specific value
               has been passed in.

           In other words, given:

               my $arg_ref = {
                   key_1 => 'generic value 1',
                   key_2 => 'generic value 2',

                   'Base::Class' => {
                       key_1 => 'base value 1'
                   },

                   'Der::Class' => {
                       key_1 => 'der value 1'
                       key_2 => 'der value 2'
                   },
               };

               package Base::Class;
               use Class::Std::Utils;

               my %base_args = extract_initializers_from($arg_ref);

               package Der::Class;
               use Class::Std::Utils;

               my %der_args = extract_initializers_from($arg_ref);

           then %base_args would be initialized to:

               (
                   key_1 => 'base value 1',
                   key_2 => 'generic value 2',

                   'Base::Class' => {
                       key_1 => 'base value 1',
                   },

                   'Der::Class' => {
                       key_1 => 'der value 1',
                       key_2 => 'der value 2',
                   },
               )

           whilst %der_args would be initialized to:

               (
                   key_1 => 'der value 1',
                   key_2 => 'der value 2',

                   'Base::Class' => {
                       key_1 => 'base value 1',
                   },

                   'Der::Class' => {
                       key_1 => 'der value 1',
                       key_2 => 'der value 2',
                   },
               )

           That is, the top-level entries would be replaced by any second-level entries with the same key that
           appear in a top-level entry of the same name as the calling package.

           This means that each class can just refer to $args{key_1} and $args{key_2} and be confident that the
           resulting values will be the most specific available for that class.

DIAGNOSTICS

       "%s initializer must be a nested hash"
           Thrown by "extract_initializers_from()". You specified a top-level key that has the same name of the
           current class, but the value of that key wasn't a hash reference.

CONFIGURATION AND ENVIRONMENT

       Class::Std::Utils requires no configuration files or environment variables.

DEPENDENCIES

       Thsi module requires both the "Scalar::Util" and "List::Util" modules, which are standard in Perl 5.8 and
       available from the CPAN for earlier versions of Perl.

INCOMPATIBILITIES

       None reported.

SEE ALSO

       The "Class::Std" module

       "Perl Best Practices", O'Reilly, 2005.

BUGS AND LIMITATIONS

       No bugs have been reported.

       Please report any bugs or feature requests to "bug-class-std-utils@rt.cpan.org", or through the web
       interface at <http://rt.cpan.org>.

AUTHOR

       Damian Conway  "<DCONWAY@cpan.org>"

LICENCE AND COPYRIGHT

       Copyright (c) 2005, Damian Conway "<DCONWAY@cpan.org>". All rights reserved.

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

DISCLAIMER OF WARRANTY

       BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT
       PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER
       PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED,
       INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
       PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE
       SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

       IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY
       OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
       TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF
       THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
       RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE
       WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
       DAMAGES.