Try::Tiny::SmartCatch(3) 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'')

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) <[email protected]>
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.

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