NAME Error::Hierarchy - Support for hierarchical exception classes VERSION version 1.103530 SYNOPSIS package Error::Hierarchy::ReadOnlyAttribute; use warnings; use strict; use base 'Error::Hierarchy'; __PACKAGE__->mk_accessors(qw(attribute)); use constant default_message => '[%s] is a read only attribute'; use constant PROPERTIES => ( 'attribute' ); # Meanwhile... package main; use Error::Hierarchy::Mixin; sub foo { if (@_) { Error::Hierarchy::ReadOnlyAttribute-> throw(attribute => 'foo'); } } DESCRIPTION This class provides support for hierarchical exception classes. It builds upon Error and is thus compatible with its "try"/"catch" mechanism. However, it records a lot more information such as the package, filename and line where the exception occurred, a complete stack trace, the hostname and a UUID. It provides a stringification that is extensible with any properties your own exceptions might define. METHODS depth Get or set the caller depth, that is the number of call stack frames that are skipped when reporting the package, filename and line the error was thrown from. When an exception object is constructed, it defaults to 0. This is useful if you want to throw an exception from the perspective of your own caller. For example: sub assert_foo { unless ($teh_foo) { throw SomeException(depth => 1); } } Without the "depth" argument, the exception would show that it was thrown within "assert_foo()". Maybe that's what you want, but with "depth()" you can make it appear as if the exception was thrown from the place where "assert_foo()" was called from. The actual exception depth is influenced by "error_depth()" as well. error_depth Like "depth()", but here the value should be defined within the exception class code itself. Therefore, you can't set the value, but subclasses can override it. Some exceptions should always be thrown from the caller's perspective (or even higher up); use "error_depth()" for this case. "depth()" by contrast is intended for the user to be set; the two are added together to get the actual depth. In this class the "error_depth()" defaults to 1 so the exception is at least reported from the place where it was actually thrown - a value of 0 would mean that the exception is reported as having occurred Error::Hierarchy itself, which is probably not what you want. If you override this value in a subclass, it's probably a good idea to add the subclass' desired depth to the superclass's depth to accumulate it. For example: package MyException; use base 'Error::Hierarchy'; sub error_depth { my $self = shift; 1 + $self->SUPER::error_depth(); } comparable Support for Data::Comparable. init Initializes a newly constructed exception object. get_properties Actual exception classes will subclass this class and define properties. Exception classes themselves can be subclassed. So this method returns the inherited list of all the exception class' properties. properties_as_hash Constructs a hash whose keys are the exception's properties - see "get_properties()" - and whose values are the values of each property in the exception object. The properties "package", "filename" and "line" are omitted. In list context, the hash is returned as is. In scalar context, a reference to the hash is returned. stringify Defines how the exception should look if the object is stringified. This class inherits from Error::Hierarchy::Base, which overloads "" to call "stringify()". This class stringifies an itself by taking the "message()" attribute and passing it to "sprintf()", along with the exception's properties. transmute($exception, %args) Transmutes an existing exception. It leaves the stack trace, filename, line etc. as it is and just blesses it into the class on which "transmute()" was called, adding the given additional arguments. This is used when catching a generic exception and turning it into a more specific one. INSTALLATION See perlmodinstall for information and options on installing Perl modules. BUGS AND LIMITATIONS No bugs have been reported. Please report any bugs or feature requests through the web interface at . AVAILABILITY The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit to find a CPAN site near you, or see . The development version lives at and may be cloned from . Instead of sending patches, please fork this project using the standard git and github infrastructure. AUTHOR Marcel Gruenauer COPYRIGHT AND LICENSE This software is copyright (c) 2004 by Marcel Gruenauer. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.