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Exception::Class::Base(3pm) User Contributed Perl Documentation Exception::Class::Base(3pm)
NAME
Exception::Class::Base - A base class for exception objects
VERSION
version 1.45
SYNOPSIS
use Exception::Class 'MyException';
eval { MyException->throw( error => 'I feel funny.' ) };
print $@->error;
DESCRIPTION
This class is the base class for all exceptions created by Exception::Class. It provides
a number of methods for getting information about the exception.
METHODS
MyException->Trace($boolean)
Each "Exception::Class::Base" subclass can be set individually to include a stacktrace
when the "as_string" method is called. The default is to not include a stacktrace. Calling
this method with a value changes this behavior. It always returns the current value
(after any change is applied).
This value is inherited by any subclasses. However, if this value is set for a subclass,
it will thereafter be independent of the value in "Exception::Class::Base".
Do not call this on the "Exception::Class::Base" class directly or you'll change it for
all exception classes that use Exception::Class, including ones created in modules you
don't control.
This is a class method, not an object method.
MyException->UnsafeRefCapture($boolean)
When a "Devel::StackTrace" object is created, it walks through the stack and stores the
arguments which were passed to each subroutine on the stack. If any of these arguments are
references, then that means that the "Devel::StackTrace" ends up increasing the ref count
of these references, delaying their destruction.
Since "Exception::Class::Base" uses "Devel::StackTrace" internally, this method provides a
way to tell "Devel::StackTrace" not to store these references. Instead,
"Devel::StackTrace" replaces references with their stringified representation.
This method defaults to false. As with "Trace", it is inherited by subclasses but setting
it in a subclass makes it independent thereafter.
Do not call this on the "Exception::Class::Base" class directly or you'll change it for
all exception classes that use Exception::Class, including ones created in modules you
don't control.
MyException->RespectOverload($boolean)
When a "Devel::StackTrace" object stringifies, by default it ignores stringification
overloading on any objects being dealt with.
Since "Exception::Class::Base" uses "Devel::StackTrace" internally, this method provides a
way to tell "Devel::StackTrace" to respect overloading.
This method defaults to false. As with "Trace", it is inherited by subclasses but setting
it in a subclass makes it independent thereafter.
Do not call this on the "Exception::Class::Base" class directly or you'll change it for
all exception classes that use Exception::Class, including ones created in modules you
don't control.
MyException->MaxArgLength($boolean)
When a "Devel::StackTrace" object stringifies, by default it displays the full argument
for each function. This parameter can be used to limit the maximum length of each
argument.
Since "Exception::Class::Base" uses "Devel::StackTrace" internally, this method provides a
way to tell "Devel::StackTrace" to limit the length of arguments.
This method defaults to 0. As with "Trace", it is inherited by subclasses but setting it
in a subclass makes it independent thereafter.
Do not call this on the "Exception::Class::Base" class directly or you'll change it for
all exception classes that use Exception::Class, including ones created in modules you
don't control.
MyException->Fields
This method returns the extra fields defined for the given class, as a list.
Do not call this on the "Exception::Class::Base" class directly or you'll change it for
all exception classes that use Exception::Class, including ones created in modules you
don't control.
MyException->throw( $message )
MyException->throw( message => $message )
MyException->throw( error => $error )
This method creates a new object with the given error message. If no error message is
given, this will be an empty string. It then dies with this object as its argument.
This method also takes a "show_trace" parameter which indicates whether or not the
particular exception object being created should show a stacktrace when its "as_string"
method is called. This overrides the value of "Trace" for this class if it is given.
The frames included in the trace can be controlled by the "ignore_class" and
"ignore_package" parameters. These are passed directly to Devel::Stacktrace's constructor.
See "Devel::Stacktrace" for more details. This class always passes "__PACKAGE__" for
"ignore_class" and 'Exception::Class' for "ignore_package", in addition to any arguments
you provide.
If only a single value is given to the constructor it is assumed to be the message
parameter.
Additional keys corresponding to the fields defined for the particular exception subclass
will also be accepted.
MyException->new(...)
This method takes the same parameters as "throw", but instead of dying simply returns a
new exception object.
This method is always called when constructing a new exception object via the "throw"
method.
MyException->description
Returns the description for the given "Exception::Class::Base" subclass. The
"Exception::Class::Base" class's description is "Generic exception" (this may change in
the future). This is also an object method.
$exception->rethrow
Simply dies with the object as its sole argument. It's just syntactic sugar. This does
not change any of the object's attribute values. However, it will cause "caller" to
report the die as coming from within the "Exception::Class::Base" class rather than where
rethrow was called.
Of course, you always have access to the original stacktrace for the exception object.
$exception->message
$exception->error
Returns the error/message associated with the exception.
$exception->pid
Returns the pid at the time the exception was thrown.
$exception->uid
Returns the real user id at the time the exception was thrown.
$exception->gid
Returns the real group id at the time the exception was thrown.
$exception->euid
Returns the effective user id at the time the exception was thrown.
$exception->egid
Returns the effective group id at the time the exception was thrown.
$exception->time
Returns the time in seconds since the epoch at the time the exception was thrown.
$exception->package
Returns the package from which the exception was thrown.
$exception->file
Returns the file within which the exception was thrown.
$exception->line
Returns the line where the exception was thrown.
$exception->context_hash
Returns a hash reference with the following keys:
o time
o pid
o uid
o euid
o gid
o egid
$exception->field_hash
Returns a hash reference where the keys are any fields defined for the exception class and
the values are the values associated with the field in the given object.
$exception->trace
Returns the trace object associated with the object.
$exception->show_trace($boolean)
This method can be used to set whether or not a stack trace is included when the as_string
method is called or the object is stringified.
$exception->as_string
Returns a string form of the error message (something like what you'd expect from die). If
the class or object is set to show traces then then the full trace is also included. The
result looks like "Carp::confess".
$exception->full_message
Called by the "as_string" method to get the message. By default, this is the same as
calling the "message" method, but may be overridden by a subclass. See below for details.
LIGHTWEIGHT EXCEPTIONS
A lightweight exception is one which records no information about its context when it is
created. This can be achieved by setting "$class->NoContextInfo" to a true value.
You can make this the default for a class of exceptions by setting it after creating the
class:
use Exception::Class (
'LightWeight',
'HeavyWeight',
);
LightWeight->NoContextInfo(1);
A lightweight exception does have a stack trace object, nor does it record the time, pid,
uid, euid, gid, or egid. It only has a message.
OVERLOADING
"Exception::Class::Base" objects are overloaded so that stringification produces a normal
error message. This just calls the "$exception->as_string" method described above. This
means that you can just "print $@" after an "eval" and not worry about whether or not its
an actual object. It also means an application or module could do this:
$SIG{__DIE__} = sub { Exception::Class::Base->throw( error => join '', @_ ); };
and this would probably not break anything (unless someone was expecting a different type
of exception object from "die").
OVERRIDING THE as_string METHOD
By default, the "as_string" method simply returns the value "message" or "error" param
plus a stack trace, if the class's "Trace" method returns a true value or "show_trace" was
set when creating the exception.
However, once you add new fields to a subclass, you may want to include those fields in
the stringified error.
Inside the "as_string" method, the message (non-stack trace) portion of the error is
generated by calling the "full_message" method. This can be easily overridden. For
example:
sub full_message {
my $self = shift;
my $msg = $self->message;
$msg .= " and foo was " . $self->foo;
return $msg;
}
SUPPORT
Bugs may be submitted at <https://github.com/houseabsolute/Exception-Class/issues>.
I am also usually active on IRC as 'autarch' on "irc://irc.perl.org".
SOURCE
The source code repository for Exception-Class can be found at
<https://github.com/houseabsolute/Exception-Class>.
AUTHOR
Dave Rolsky <autarch AT urth.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2021 by Dave Rolsky.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.
The full text of the license can be found in the LICENSE file included with this
distribution.
perl v5.32.1 2021-09-12 Exception::Class::Base(3pm)
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On Apache
Under GNU General Public License
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