NAME¶

Ouch - Exceptions that don't hurt.

VERSION¶

version 0.0401

SYNOPSIS¶

 use Ouch;
 eval { ouch(404, 'File not found.'); };
 if (kiss 404) {
   check_elsewhere();
 }
 say $@;           # These two lines do the
 say $@->scalar;   # same thing.

DESCRIPTION¶

Ouch provides a class for exception handling that doesn't require a lot of boilerplate, nor any up front definition. If Exception::Class is working for you, great! But if you want something that is faster, easier to use, requires less typing, and has no prereqs, but still gives you much of that same functionality, then Ouch is for you.

Why another exception handling module?¶

It really comes down to Carp isn't enough for me, and Exception::Class does what I want but makes me type way too much. Also, I tend to work on a lot of protocol-based systems that use error codes (HTTP, FTP, SMTP, JSON-RPC) rather than error classes, so that feels more natural to me. Consider the difference between these: Ouch

 use Ouch;
 ouch 404, 'File not found.', 'file';

Exception::Class

 use Exception::Class (
    'FileNotFound' => {
        fields  => [ 'code', 'field' ],
    },
 );
 FileNotFound->throw( error => 'File not found.', code => 404, field => 'file' );

And if you want to catch the exception you're looking at: Ouch

 if (kiss 404) {
   # do something
 }

Exception::Class

 my $e;
 if ($e = Exception::Class->caught('FileNotFound')) {
   # do something
 }

Those differences may not seem like a lot, but over any substantial program with lots of exceptions it can become a big deal.

Usage¶

Most of the time, all you need to do is:

 ouch $code, $message, $data;
 ouch -32700, 'Parse error.', $request; # JSON-RPC 2.0 error
 ouch 441, 'You need to specify an email address.', 'email'; # form processing error
 ouch 'missing_param', 'You need to specify an email address.', 'email';

You can also go long form if you prefer:

 die Ouch->new($code, $message, $data);

Functional Interface¶

ouch Some nice sugar instead of using the object oriented interface.

 ouch 2121, 'Did not do the big thing.';

code

An error code. An integer or string representing error type. Try to stick to codes used in whatever domain you happen to be working in. HTTP Status codes. JSON-RPC error codes, etc.

message

A human readable error message.

data

Optional. Anything you want to attach to the exception to help a developer catching it decide what to do. For example, if you're doing form processing, you might want this to be the name of the field that caused the exception.

 

WARNING: Do not include objects or code refs in your data. This should only be stuff that is easily serializable like scalars, array refs, and hash refs.

kiss Some nice sugar to trap an Ouch.

 if (kiss $code) {
    # make it go
 }

code

The code you're looking for.

exception

Optional. If you like you can pass the exception into "kiss". If not, it will just use whatever is in $@. You might want to do this if you've saved the exception before running another "eval", for example.

hug Some nice sugar to trap any exception.

 if (hug) {
   # make it stop
 }

exception

Optional. If you like you can pass the exception into "hug". If not, it will just use whatever is in $@.

bleep A little sugar to make exceptions human friendly. Returns a clean error message from any exception, including an Ouch.

 File not found.

Rather than:

 File not found. at /Some/File.pm line 63.

exception

Optional. If you like you can pass the exception into "bleep". If not, it will just use whatever is in $@.

Calls "bleep", and then exits with error code

exception

Optional. You can pass an exception into "barf" which then gets passed to "bleep" otherwise it will use whatever's in $@

Object-Oriented Interface¶

new Constructor for the object-oriented interface. Takes the same parameters as "ouch".

 Ouch->new($code, $message, $data);

scalar Returns the scalar form of the error message:

 Crap! at /Some/File.pm line 43.

Just as if you had done:

 die 'Crap!';

Rather than:

 ouch $code, 'Crap!';

trace Call this if you want the full stack trace that lead up to the ouch. hashref Returns a formatted hash reference of the exception, which can be useful for handing off to a serializer like JSON.

 {
   code     => $code,
   message  => $message,
   data     => $data,
 }

code Returns the "code" passed into the constructor. message Returns the "messsage" passed into the constructor. data Returns the "data" passed into the constructor.

Traditional Interface¶

Some people just can't bring themselves to use the sugary cuteness of Ouch. For them there is the ":traditional" interface. Here's how it works:

 use Ouch qw(:traditional);
 my $e = try {
   throw 404, 'File not found.';
 };
 if ( catch 404, $e ) {
   # do the big thing
 }
 elsif ( catch_all $e ) {
   # make it stop
 }
 else {
   # make it go
 }

NOTE: "try" also populates $@, and "catch" and "catch_all" will also use $@ if you don't specify an exception. try Returns an exception. Is basically just a nice wrapper around "eval".

block

Try accepts a code ref, anonymous subroutine, or a block.

 

NOTE: You need a semi-colon at the end of a "try" block.

throw Works exactly like "ouch". See "ouch" for details. catch Works exactly like "kiss". See "kiss" for details. catch_all Works exactly like "hug". See "hug" for details.

Try::Tiny¶

Many Ouch users, like to use Ouch with Try::Tiny, and some of them are sticks in the mud who can't bring themselves to "ouch" and "kiss", and don't like that ":traditional" walks all over "try" and "catch" For them, there is the ":trytiny" interface. Here's how it works:

 use Try::Tiny;
 use Ouch qw(:trytiny);
 try {
    throw(404, 'File not found!';
 }
 catch {
    if (caught($_)) {
        # do something
    }
    else {
        throw($_); # rethrow
    }
 };

SUPPORT¶

Repository

<http://github.com/rizen/Ouch>

Bug Reports

<http://github.com/rizen/Ouch/issues>

SEE ALSO¶

If you're looking for something lighter, check out Carp that ships with Perl. Or if you're looking for something heavier check out Exception::Class.

AUTHOR¶

JT Smith <jt_at_plainblack_dot_com>

LEGAL¶

Ouch is Copyright 2011 Plain Black Corporation (<http://www.plainblack.com>) and is licensed under the same terms as Perl itself.