oracular (3) Lexical::Failure::Objects.3pm.gz

NAME

       Lexical::Failure::Objects - Special failure objects for Lexical::Failure

VERSION

       This document describes Lexical::Failure::Objects version 0.000001

DESCRIPTION

       This module implements the "failure objects" returned by the optional 'failobj' mechanism of the
       "Lexical::Failure" module.

       When "ON_FAILURE 'failobj'" is in effect, any call to "fail" will return one of these objects, which
       simulates a special out-of-band value that you can either explicitly test for failure or else simply
       ignore and automatically get an exception.

       For example, given the subroutine:

           package Math;
           use Lexical::Failure;

           sub inverse_square {
               my ($n) = @_;

               if ($n == 0) {
                   fail "Can't invert zero";
               }

               return 1/$n**2;
           }

       when 'failobj' is the selected failure signalling strategy:

           use Math (fail => 'failobj')

       then failure can either be tested for explicitly:

           # This block skipped if $n == 0...
           if (my $inv_sq = Math::inverse_square($n) {
               print $inv_sq;
           }

       or else simply ignored, in which case an exception will automatically be thrown:

           print inverse_square($n);    # ...throw exception if $n == 0

INTERFACE

       If it is used as a boolean, a failure object evaluates false (i.e. it acts as if "ON_FAILURE 'undef'" had
       been in effect).

       If it is used as a value in any other way (as a string, as a reference, as a regex, as a filehandle,
       etc., etc.), or if it's ignored and allowed to go out of scope without being evaluated at all, then a
       failure object throws an exception (i.e. it acts as if "ON_FAILURE 'croak'" had been in effect).

   Constructor ("new()")
       The class's constructor expects two named arguments:

           $failure_obj = Lexical::Failure::Objects->new(
                              msg     => $MESSAGE_STR_OR_OBJ,
                              context => [$PACKAGE, $FILE, $LINE, $SUBNAME],
                          );

       You should never normally need to construct failure objects directly; it's better to let
       "Lexical::Failure" craete them automatically via its 'failobj' mechanism.

   Methods
       "Lexical::Failure::Objects" also provides four methods with which you can query the location of the
       failure that they represent. None of these methods takes any arguments.

       "$failobj->subname()"
           Returns the name of the subroutine in which the failure was signaled.  That is, the equivalent of
           "(caller 0)[3]".

       "$failobj->file()"
           Returns the name of the file containing the subroutine call from which failure was signaled.  That
           is, the equivalent of "(caller 0)[1]".

       "$failobj->line()"
           Returns the line number of the subroutine call from which failure was signaled.  That is, the
           equivalent of "(caller 0)[2]".

       "$failobj->context()"
           Returns a string summarizing the information provided by the previous three methods, in the form:

               "call to <subname> at <file> line <line>"

DIAGNOSTICS

       None of their own.

       If they throw an exception (when misused or ignored), it will be the exception that "fail" would
       otherwise have thrown.

CONFIGURATION AND ENVIRONMENT

       Lexical::Failure::Objects requires no configuration files or environment variables.

DEPENDENCIES

       Requires the Hash::Util::FieldHash module.

INCOMPATIBILITIES

       None reported.

BUGS AND LIMITATIONS

       No bugs have been reported.

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

AUTHOR

       Damian Conway  "<DCONWAY@cpan.org>"

LICENCE AND COPYRIGHT

       Copyright (c) 2013, 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. See perlartistic.

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.