NAME
   Getopt::O2 - Command line argument processing and automated help
   generation, object oriented

SYNOPSIS
     package MyPackage;
     use base 'Getopt::O2';

     # return a short descriptive string about the program (appears in --help)
     sub getProgramDescription
         {
             'A sample program'
         }

     # return rules about parameters
     sub getOptionRules
         {
             shift->SUPER::getOptionRules(),
                 'length=i' => ['A numeric argument', 'default' => 33],
                 'file=s'   => ['A text argument'],
                 'quiet'    => ['A "flag" argument'];
         }

     # read options
     new MyPackage->getopt(\%options);

DESCRIPTION
   The "Getopt::O2" module implements an extended "Getopt" class which
   parses the command line from @ARGV, recognizing and removing specified
   options and their possible values.

   This function adheres to the POSIX syntax for command line options, with
   GNU extensions. In general, this means that options have long names
   instead of single letters, and are introduced with a double dash "--".
   Support for bundling of command line options, as was the case with the
   more traditional single-letter approach, is provided.

 Methods
   *PACKAGE*->getopt(*HASHREF*)
       Processes command line options and stores their values in the hash
       reference passed as its argument.

   *PACKAGE*->getOptionRules()
       Returns a list of rules of command line options. The base package
       provides two options "--help" and "--verbose" by default. The former
       calls "usage()"; the latter is an *incremental option*. See "Writing
       Rules" for what your implementation should return.

   *PACKAGE*->getProgramDescription()
       Returns a short descriptive string about the program's
       functionality. This string is used as a caption of the generated
       program usage text.

   *PACKAGE*->usage(*CODE [, MESSAGE [, LIST ] ]*)
       Display program usage summary and exit with status "CODE". Without
       any further arguments it will show the program's description text.
       If given, "MESSAGE" will be treated as an "sprintf()"-like formatter
       string followed by its arguments and prefixed with "Error: ".

   *PACKAGE*->error(*MESSAGE [, LIST ]*)
       This method is called internally when processing or validation of
       options failed and does nothing but passing its arguments to
       "usage()" (along with an exit code of 1). Override this method if
       you require other methods of error handling.

 Writing Rules
   Command line options are processed using rules returned the
   "getOptionsRules()" implementation. Rules are expressed much like with
   Getopt::Long. A rule expression is followed by the rule's help string
   and possible options.

   The options must be represented as either a string (used as help string)
   or an ARRAYREF. The first element of the latter is used as the options'
   help string. Its second element can be a CODEREF which is called when
   the option was seen. The rest are key-value-pairs that are coerced to a
   hash. A single "undef" can be used to separate option categories (used
   in "usage()").

         # Short variant. Define flag and its help string
         'q|quiet' => 'Suppresses informational program output'

         # Actual implementation of "--help" parameter
         'h|help' => ['Display this help message', sub {
             $self->usage()
         }]

         # Use callback return value as option value
         'l|limit=i' => ['Limit amount of things', sub {
             my ($arg, $key) = @_;
             $arg = 100 if $arg > 100;
             return $arg; # make sure --limit is not larger than 100
         }]

         # Enumeration with allowed values
         'o|output=?' => ['Use ARG as output format', 'values' => [qw(xml html json)]]

 Rule syntax
   !w|warnings
       Defines a *negatable option*. The value of it will be a "boolean" in
       the resulting options hash reference depending on whether
       "--warnings" or "--no-warnings" was seen on the command line.
       There's no short negatable option.

   v|verbose+
       Defines an *incremental option*. Depending on how often it's seen on
       the command line, the option's value will increase in the resulting
       hashref.

   q|quiet
       Defines a *flag option*. The flag will be set in the resulting
       hashref if this option was seen on the command line.

   f|filename=s
       Defines an *option with a mandatory value*. The character after the
       "=" sign determines the expected value: "s" is a generic string, "i"
       is a numeric value (it uses Perl's looks_like_number) and "?" is an
       enumeration. If the type specifier is suffixed with a "@", the
       resulting value will be an ARRAYREF with all values.

       Enumerations must provide a "values" option which must be an
       ARRAYREF of valid values for the option. They may use the
       "keep_unique" option which defaults to being set in order to control
       whether the resulting list contains unique values or all given
       values.

TODO
DEPENDENCIES
   None special. Uses core perl libraries.

AUTHOR
   Oliver Schieche <[email protected]>

   http://perfect-co.de/

   $Id: O2.pm 888 2019-09-01 20:36:34Z schieche $

LICENSE AND COPYRIGHT
   Copyright 2013-2019 Oliver Schieche.

   This software is a free library. You can modify and/or distribute it
   under the same terms as Perl itself.

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