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Try-Tiny-SmartCatch-0.5
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/ Try::Tiny::SmartCatch

NAME

Try::Tiny::SmartCatch - lightweight Perl module for powerful exceptions handling

VERSION

Version 0.5

SYNOPSIS

use Try::Tiny::SmartCatch;

try sub {}, # at least one try block
catch_when 'ExceptionName' => sub {}, # zero or more catch_when blocks
catch_when 'exception message' => sub {},
catch_when qr/exception  message regexp/ => sub {},
catch_default sub {}, # zero or one catch_default block
then sub {}, # if no exception is raised, execute then block
finally sub {}; #zero or more finally blocks

use Try::Tiny::SmartCatch qw/throw/; # import only throw
# You can import also all function at once:
# use Try::Tiny::SmartCatch qw/:all/;
throw('some exception');
throw(SomeException->new ('message'));

DESCRIPTION

Goals are mostly the same as Try::Tiny module, but there are few changes to it's specification. Main difference is possibility to catch just some kinds of exceptions in place of catching everything. Another one is slightly changed syntax.

When raised exception is an object, Try::Tiny::SmartCatch will test for exception type (using UNIVERSAL::isa). When raised exception is just a text message (like: die ('message')), there can be specified part of message to test for.

There are also explicit sub blocks. In opposite to Try::Tiny, every block in Try::Tiny::SmartCatch: try, catch_when, catch_default, then and finally must have explicit subroutines specified. Thanks to trick with function prototype, calling Try::Tiny::try or Try::Tiny::catch creates implicit subroutines:

sub test_function {
    try {
        # yes, here is implicit subroutine!
        # return statement here exits just from try block,
        # not from test_function!
        return 1;
    };

    say 'Hello!';
}

test_function();

Above snippet produces us text on STDOUT: Hello!

But more obvious would be no output... (by return statement). This is because of implicit subroutine created with braces: {} after try, catch or finally from Try::Tiny. Try::Tiny::SmartCatch is more explicit - you must always use sub when defining blocks (look at [Syntax](#Syntax) above).

An exception object or message is passed to defined blocks in two ways: * in $_ variable * as function arguments, so through @_ array.

Try::Tiny::SmartCatch defines also throw function (not imported by default). Currently it is an alias for die, but is more explicit then die :)

It can be imported separately:

use Try::Tiny::SmartCatch qw/throw/;

Or with rest of functions:

use Try::Tiny::SmartCatch qw/:all/;

EXPORT

By default exported are functions:

try
catch_when
catch_default
then
finally

You can also explicit import throw function:

use Try::Tiny::SmartCatch qw/throw/;

Or all functions at all:

use Try::Tiny::SmartCatch qw/:all/;

SUBROUTINES/METHODS

try($;@)

Works like Try::Tiny try subroutine, here is nothing to add :)

The only difference is that here must be given evident sub reference, not anonymous block:

try sub {
    # some code
};

catch_when($$;@)

Intended to be used in the second argument position of try.

Works similarly to Try::Tiny catch subroutine, but have a little different syntax:

try sub {
    # some code
},
catch_when 'Exception1' => sub {
    # catch only Exception1 exception
},
catch_when ['Exception1', 'Exception2'] => sub {
    # catch Exception2 or Exception3 exceptions
};

If raised exception is a blessed reference (or object), Exception1 means that exception class has to be or inherits from Exception1 class. In other case, it search for given string in exception message (using index function or regular expressions - depending on type of given operator). For example:

try sub {
    throw('some exception message');
},
catch_when 'exception' => sub {
    say 'exception caught!';
};

Other case:

try sub {
    throw('some exception3 message');
},
catch_when qr/exception\d/ => sub {
    say 'exception caught!';
};

Or:

try sub {
    # ValueError extends RuntimeError
    throw(ValueError->new ('Some error message'));
},
catch_when 'RuntimeError' => sub {
    say 'RuntimeError exception caught!';
};

catch_default($;@)

Works exactly like Try::Tiny catch function (OK, there is difference: need to specify evident sub block instead of anonymous block):

try sub {
    # some code
},
catch_default sub {
    say 'caught every exception';
};

then($;@)

then block is executed after try clause, if none of catch_when or catch_default blocks was executed (it means, if no exception occured). It's executed before finally blocks.

try sub {
    # some code
},
catch_when 'MyException' => sub {
    say 'caught MyException exception';
},
then sub {
    say 'No exception was raised';
},
finally sub {
    say 'executed always';
};

finally($;@)

Works exactly like Try::Tiny finally function (OK, again, explicit sub instead of implicit):

try sub {
    # some code
},
finally sub {
    say 'executed always';
};

throw

Currently it's an alias to die function, but throw is more obvious then die when working with exceptions :)

In future it also can do more then just call die.

It's not exported by default (see: "EXPORT")

SEE ALSO

https://github.com/mysz/try-tiny-smartcatch

Try::Tiny::SmartCatch home.

Try::Tiny

Minimal try/catch with proper localization of $@, base of Try::Tiny::SmartCatch

TryCatch

First class try catch semantics for Perl, without source filters.

AUTHOR

Marcin Sztolcman, <marcin at urzenia.net>

BUGS

Please report any bugs or feature requests through the web interface at http://github.com/mysz/try-tiny-smartcatch/issues.

SUPPORT

You can find documentation for this module with the perldoc command.

perldoc Try::Tiny::SmartCatch

You can also look for information at:

ACKNOWLEDGEMENTS

Yuval Kogman

for his Try::Tiny module

mst - Matt S Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>

for good package name and few great features

LICENSE AND COPYRIGHT

Copyright (c) 2012-2013 Marcin Sztolcman. All rights reserved.

Base code is borrowed from Yuval Kogman L<Try::Tiny> module,
released under MIT License.

This program is free software; you can redistribute
it and/or modify it under the terms of the MIT license.