/ 
Error-Hierarchy-0.07
River stage one • 6 direct dependents • 6 total dependents
/ Error::Hierarchy

NAME

Error::Hierarchy - Support for hierarchical exception classes

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.

acknowledged
$obj->acknowledged($value);
my $value = $obj->acknowledged;

If called without an argument, returns the boolean value (0 or 1). If called with an argument, it normalizes it to the boolean value. That is, the values 0, undef and the empty string become 0; everything else becomes 1.

acknowledged_clear
$obj->acknowledged_clear;

Clears the boolean value by setting it to 0.

acknowledged_set
$obj->acknowledged_set;

Sets the boolean value to 1.

clear_acknowledged
$obj->clear_acknowledged;

Clears the boolean value by setting it to 0.

clear_is_optional
$obj->clear_is_optional;

Clears the boolean value by setting it to 0.

is_optional
$obj->is_optional($value);
my $value = $obj->is_optional;

Defines whether the exception is optional or mandatory. This isn't really part of the exception itself, it has to do more with how you process the exception. You might want to treat some exceptions as more important than others. But it's nice to be able to set it within the exception object.

If called without an argument, returns the boolean value (0 or 1). If called with an argument, it normalizes it to the boolean value. That is, the values 0, undef and the empty string become 0; everything else becomes 1.

is_optional_clear
$obj->is_optional_clear;

Clears the boolean value by setting it to 0.

is_optional_set
$obj->is_optional_set;

Sets the boolean value to 1.

set_acknowledged
$obj->set_acknowledged;

Sets the boolean value to 1.

set_is_optional
$obj->set_is_optional;

Sets the boolean value to 1.

Error::Hierarchy inherits from Error::Hierarchy::Base.

The superclass Error::Hierarchy::Base defines these methods and functions:

new(), dump_as_yaml(), dump_raw()

The superclass Error defines these methods and functions:

_throw_Error_Simple(), associate(), catch(), file(), flush(), import(),
object(), prior(), record(), text(), throw(), value(), with()

The superclass Data::Inherited defines these methods and functions:

every_hash(), every_list(), flush_every_cache_by_key()

The superclass Class::Accessor::Complex defines these methods and functions:

mk_abstract_accessors(), mk_array_accessors(), mk_boolean_accessors(),
mk_class_array_accessors(), mk_class_hash_accessors(),
mk_class_scalar_accessors(), mk_concat_accessors(),
mk_forward_accessors(), mk_hash_accessors(), mk_integer_accessors(),
mk_new(), mk_object_accessors(), mk_scalar_accessors(),
mk_set_accessors(), mk_singleton()

The superclass Class::Accessor defines these methods and functions:

_carp(), _croak(), _mk_accessors(), accessor_name_for(),
best_practice_accessor_name_for(), best_practice_mutator_name_for(),
follow_best_practice(), get(), make_accessor(), make_ro_accessor(),
make_wo_accessor(), mk_accessors(), mk_ro_accessors(),
mk_wo_accessors(), mutator_name_for(), set()

The superclass Class::Accessor::Installer defines these methods and functions:

install_accessor()

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests through the web interface at http://rt.cpan.org.

INSTALLATION

See perlmodinstall for information and options on installing Perl modules.

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find a CPAN site near you. Or see http://search.cpan.org/dist/Error-Hierarchy/.

AUTHORS

Marcel Grünauer, <marcel@cpan.org>

COPYRIGHT AND LICENSE

Copyright 2004-2009 by the authors.

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