Exception::Class::Base - A base class for exception objects
version 1.45
use Exception::Class 'MyException';
eval { MyException->throw( error => 'I feel funny.' ) };
print $@->error;
This class is the base class for all exceptions created by the Exception::Class manpage.
It provides a number of methods for getting information about the exception.
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 the Exception::Class manpage, including
ones created in modules you don't control.
This is a class method, not an object method.
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 the Exception::Class manpage, including
ones created in modules you don't control.
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 the Exception::Class manpage, including
ones created in modules you don't control.
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 the Exception::Class manpage, including
ones created in modules you don't control.
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 the Exception::Class manpage, including
ones created in modules you don't control.
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.
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.
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.
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.
Returns the error/message associated with the exception.
Returns the pid at the time the exception was thrown.
Returns the real user id at the time the exception was thrown.
Returns the real group id at the time the exception was thrown.
Returns the effective user id at the time the exception was thrown.
Returns the effective group id at the time the exception was thrown.
Returns the time in seconds since the epoch at the time the exception was
thrown.
Returns the package from which the exception was thrown.
Returns the file within which the exception was thrown.
Returns the line where the exception was thrown.
Returns a hash reference with the following keys:
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.
Returns the trace object associated with the object.
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.
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 .
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.
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.
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 C<print $@> after an
C<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 ).
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;
}
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 .
The source code repository for Exception-Class can be found at https://github.com/houseabsolute/Exception-Class.
Dave Rolsky <autarch@urth.org>
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.
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