--- name: "Ouch" section: "3pm" platform: "linux" package: "libouch-perl" version: "0.0501-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/Ouch" --- # Ouch(3pm) Exceptions that don't hurt. ## NAME Ouch - Exceptions that don't hurt. ## VERSION version 0.0501 ## 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); ``` If you want to rethrow an Ouch, you can simply `"die"` it. ``` eval { ouch(404, 'File not found.'); } ; die $@; ``` ### 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 `$@`. *bleep* A little sugar to make exceptions human friendly. Returns a clean error message from any exception, including an Ouch. ``` File not found. ``` Rather than: ``` File not found. at /Some/File.pm line 63. ``` - exception Optional. If you like you can pass the exception into `"bleep"`. If not, it will just use whatever is in `$@`. *barf* 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. ### Try::Tiny Many Ouch users like to use Ouch with Try::Tiny. ``` use Try::Tiny; use Ouch; try { ouch 404, 'File not found!'; } catch { if (kiss(401, $_)) { # do something } else { die $_; # rethrow } }; ``` Some users are sticks in the mud who can't bring themselves to `"ouch"` and `"kiss"`. 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(401, $_)) { # do something } else { die $_; # rethrow } }; ``` Using Try::Tiny has some impedence mismatch in that the exception is propagated through `$_` instead of `$@` (the default used by Ouch). This forces to always include `$_` when calling functions in Ouch, which is suboptimal. It's possible to do this: ``` use Try::Tiny; use Ouch qw(:trytiny_var); # use Try::Tiny's variable $_ try { throw 404, 'File not found!'; } catch { if (kiss 401) { # do something } else { die $_; # rethrow } }; ``` i.e. you can use the regular Ouch syntax. This behaviour is localized to the import, i.e. if Ouch is then imported in another place it is possible to decide again which is the default exception variable in that specific import: ``` package I::Want::Try::Tiny; use Try::Tiny; use Ouch qw(:trytiny_var); # ... $_ is the default exception for kiss, hug, barf, and bleep package Gimme::Regular::Ouch; use Ouch; # ... $@ is the default exception object here ``` It's also possible to mix the two approaches, i.e. use both `":trytiny"` and `":trytiny_var"`. *throw* See `"ouch"` for details. *caught* See `"kiss"` for details. *caught\_all* See `"hug"` for details. ## DEPRECATED This functionality is deprecated and will be removed in a future release. Use Try::Tiny instead. ### 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. ## REQUIREMENTS Requires Perl 5.12 or higher. ## SUPPORT - Repository \ - Bug Reports \ ## 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 \ ## LEGAL Ouch is Copyright 2011 Plain Black Corporation (\) and is licensed under the same terms as Perl itself.