autodie::exception - man - phpman

NAME
    autodie::exception - Exceptions from autodying functions.

SYNOPSIS
        eval {
            use autodie;

            open(my $fh, '<', 'some_file.txt');

            ...
        };

        if (my $E = $@) {
            say "Ooops!  ",$E->caller," had problems: $@";
        }

DESCRIPTION
    When an autodie enabled function fails, it generates an "autodie::exception" object. This can be
    interrogated to determine further information about the error that occurred.

    This document is broken into two sections; those methods that are most useful to the
    end-developer, and those methods for anyone wishing to subclass or get very familiar with
    "autodie::exception".

  Common Methods
    These methods are intended to be used in the everyday dealing of exceptions.

    The following assume that the error has been copied into a separate scalar:

        if ($E = $@) {
            ...
        }

    This is not required, but is recommended in case any code is called which may reset or alter $@.

   args
        my $array_ref = $E->args;

    Provides a reference to the arguments passed to the subroutine that died.

   function
        my $sub = $E->function;

    The subroutine (including package) that threw the exception.

   file
        my $file = $E->file;

    The file in which the error occurred (eg, "myscript.pl" or "MyTest.pm").

   package
        my $package = $E->package;

    The package from which the exceptional subroutine was called.

   caller
        my $caller = $E->caller;

    The subroutine that *called* the exceptional code.

   line
        my $line = $E->line;

    The line in "$E->file" where the exceptional code was called.

   context
        my $context = $E->context;

    The context in which the subroutine was called by autodie; usually the same as the context in
    which you called the autodying subroutine. This can be 'list', 'scalar', or undefined (unknown).
    It will never be 'void', as "autodie" always captures the return value in one way or another.

    For some core functions that always return a scalar value regardless of their context (eg,
    "chown"), this may be 'scalar', even if you used a list context.

   return
        my $return_value = $E->return;

    The value(s) returned by the failed subroutine. When the subroutine was called in a list
    context, this will always be a reference to an array containing the results. When the subroutine
    was called in a scalar context, this will be the actual scalar returned.

   errno
        my $errno = $E->errno;

    The value of $! at the time when the exception occurred.

    NOTE: This method will leave the main "autodie::exception" class and become part of a role in
    the future. You should only call "errno" for exceptions where $! would reasonably have been set
    on failure.

   eval_error
        my $old_eval_error = $E->eval_error;

    The contents of $@ immediately after autodie triggered an exception. This may be useful when
    dealing with modules such as Text::Balanced that set (but do not throw) $@ on error.

   matches
        if ( $e->matches('open') ) { ... }

        if ( 'open' ~~ $e ) { ... }

    "matches" is used to determine whether a given exception matches a particular role.

    An exception is considered to match a string if:

    *   For a string not starting with a colon, the string exactly matches the package and
        subroutine that threw the exception. For example, "MyModule::log". If the string does not
        contain a package name, "CORE::" is assumed.

    *   For a string that does start with a colon, if the subroutine throwing the exception *does*
        that behaviour. For example, the "CORE::open" subroutine does ":file", ":io" and ":all".

        See "CATEGORIES" in autodie for further information.

        On Perl 5.10 and above, using smart-match ("~~") with an "autodie::exception" object will
        use "matches" underneath. This module used to recommend using smart-match with the exception
        object on the left hand side, but in future Perls that is likely to stop working. The
        smart-match facility of this class should only be used with the exception object on the
        right hand side. Having the exception object on the right is both future-proof and portable
        to older Perls, back to 5.10. Beware that this facility can only be relied upon when it is
        certain that the exception object actually is an "autodie::exception" object; it is no more
        capable than an explicit call to the "matches" method.

  Advanced methods
    The following methods, while usable from anywhere, are primarily intended for developers wishing
    to subclass "autodie::exception", write code that registers custom error messages, or otherwise
    work closely with the "autodie::exception" model.

   register
        autodie::exception->register( 'CORE::open' => \&mysub );

    The "register" method allows for the registration of a message handler for a given subroutine.
    The full subroutine name including the package should be used.

    Registered message handlers will receive the "autodie::exception" object as the first parameter.

   add_file_and_line
        say "Problem occurred",$@->add_file_and_line;

    Returns the string " at %s line %d", where %s is replaced with the filename, and %d is replaced
    with the line number.

    Primarily intended for use by format handlers.

   stringify
        say "The error was: ",$@->stringify;

    Formats the error as a human readable string. Usually there's no reason to call this directly,
    as it is used automatically if an "autodie::exception" object is ever used as a string.

    Child classes can override this method to change how they're stringified.

   format_default
        my $error_string = $E->format_default;

    This produces the default error string for the given exception, *without using any registered
    message handlers*. It is primarily intended to be called from a message handler when they have
    been passed an exception they don't want to format.

    Child classes can override this method to change how default messages are formatted.

   new
        my $error = autodie::exception->new(
            args => \@_,
            function => "CORE::open",
            errno => $!,
            context => 'scalar',
            return => undef,
        );

    Creates a new "autodie::exception" object. Normally called directly from an autodying function.
    The "function" argument is required, its the function we were trying to call that generated the
    exception. The "args" parameter is optional.

    The "errno" value is optional. In versions of "autodie::exception" 1.99 and earlier the code
    would try to automatically use the current value of $!, but this was unreliable and is no longer
    supported.

    Atrributes such as package, file, and caller are determined automatically, and cannot be
    specified.

SEE ALSO
    autodie, autodie::exception::system

LICENSE
    Copyright (C)2008 Paul Fenwick

    This is free software. You may modify and/or redistribute this code under the same terms as Perl
    5.10 itself, or, at your option, any later version of Perl 5.

AUTHOR
    Paul Fenwick <pjf AT perltraining.au>