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vars::global
try to make global variables a little safer

vars::global - try to make global variables a little safer


NAME

vars::global - try to make global variables a little safer


VERSION

This document describes vars::global version 0.0.1. But don't trust this number, see $VERSION at the very beginning of the module (you can see the source with


   perldoc -m vars::global

   

did you know?)


SYNOPSIS


    # In the place/package where we want to create globals

    use vars::global create => qw( $foo @bar %baz );

    # Add some more global symbols

    vars::global->create(qw( $hello @world %now ));

    # Somewhere else, where we need to access those globals

    use vars::global qw( $foo @bar %baz );

    # Don't try to use globals that do not exist

    use vars::global qw( $Foo ); # typo, croaks

    use vars::global qw( @inexistent ); # we don't create by default

                                        # use 'create' as above

    # You can also import and create new globals

    use vars::global qw( $foo %baz ), create => qw( $hey @joe );

    # If you're lazy, you can import all the globals defined so far

    use vars::global ':all';

  

=head1 DESCRIPTION

This module lets you define 'global' variables and gain a slight advantage over blind use of package variables.

The global variables live inside the vars::global package, with the names given by the user. Where' the advantage? It's two-fold:

  • there is an import mechanism that lets you access the global variable without the need to fully qualify its name (i.e. using $foo instead of $vars::global::foo);

  • the import mechanism ensures that you can import only the global variables that have been explicitly declared so far, which reduces the possibility of a typo.

If you have already ``created'' the global variable $foo, the import operation is equivalent to do:


   *{__PACKAGE__ . '::foo'} = \$vars::global::foo;

that is, the package variable in the current package is made an alias for the global variable.

The anti-typo check is simply obtained by doing a check before the above import.

Typical usage is as follows:

creation
Early in the module or in the program you create variables prepending the create word, as follows:

   use vars::global create => qw( $foo @bar %baz );

access
In the modules where you need to access a given global variable, you can import them very simply:

   use vars::global qw( $foo %baz ); # I don't need @bar here ;)

The creation step above automatically imports all the new globals into the current package.


INTERFACE

vars::global->import( @LIST );

Import symbols in @LIST as global variables into the current package. @LIST must contain one of the following:

  • a valid Perl variable name, i.e. an initial sigil among '$', '@' and '%', followed by a valid non-empty identifier (i.e. a string matching /\A\w+\z/);

  • the 'create' word, in which case the following items will be added to the list of valid global variables before the import

  • the ':all' string, in which case all the currently available global variables are imported.

vars::global->create( @LIST );

Add symbols in @LIST to the list of valid global variables. These symbols must be valid Perl variable names (see above for 'import').

my $ref = vars::global->has( $varname );

Check if a given simbol (contained into $varname in the example) is a global variable. Return undef if the symbol is not a currently registered global variable, otherwise it returns a reference to the variable itself.


DIAGNOSTICS

undefined symbol
Please don't pass the undef value in the import or create list, but only names of allowable Perl variables!

empty symbol
You tried to pass a bare sigil without specifing an identifier for the variable.

invalid identifier '%s'
The symbol name should consist of a sigil (any among '$', '@' and '%') followed by a string that can be considered an identifier, i.e. matching /\A\w+\z/.

invalid sigil: '%s'
What's unclear about the fact that the first character of every symbol you try to import should start with '$', '@' or '%'?!?

non existent global: '%s'
You tried to import a variable that hasn't been registered as a valid global one. Chances are that you are either forgetting to create it, or that you made a typo.


CONFIGURATION AND ENVIRONMENT

vars::global requires no configuration files or environment variables.


DEPENDENCIES

strict and warnings are almost always on, except the few points where we really need to shut them down. Complaining is made via Carp.


INCOMPATIBILITIES

None reported.


BUGS AND LIMITATIONS

Not really a bug, but it has to be noted that the import mechanism aliases package variables in the current package with those in the vars::global package. These settings are program-wide, i.e. they apply whenever and wherever you enter the package from which you imported. They're globals, and you should use them very sparingly!

No bugs have been reported.

Please report any bugs or feature requests through http://rt.cpan.org/


AUTHOR

Flavio Poletti <flavio [at] polettix [dot] it>


LICENCE AND COPYRIGHT

Copyright (c) 2006, Flavio Poletti <flavio [at] polettix [dot] it>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic and perlgpl.

Questo modulo è software libero: potete ridistribuirlo e/o modificarlo negli stessi termini di Perl stesso. Vedete anche perlartistic e perlgpl.


DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.


NEGAZIONE DELLA GARANZIA

Poiché questo software viene dato con una licenza gratuita, non c'è alcuna garanzia associata ad esso, ai fini e per quanto permesso dalle leggi applicabili. A meno di quanto possa essere specificato altrove, il proprietario e detentore del copyright fornisce questo software ``così com'è'' senza garanzia di alcun tipo, sia essa espressa o implicita, includendo fra l'altro (senza però limitarsi a questo) eventuali garanzie implicite di commerciabilità e adeguatezza per uno scopo particolare. L'intero rischio riguardo alla qualità ed alle prestazioni di questo software rimane a voi. Se il software dovesse dimostrarsi difettoso, vi assumete tutte le responsabilità ed i costi per tutti i necessari servizi, riparazioni o correzioni.

In nessun caso, a meno che ciò non sia richiesto dalle leggi vigenti o sia regolato da un accordo scritto, alcuno dei detentori del diritto di copyright, o qualunque altra parte che possa modificare, o redistribuire questo software così come consentito dalla licenza di cui sopra, potrà essere considerato responsabile nei vostri confronti per danni, ivi inclusi danni generali, speciali, incidentali o conseguenziali, derivanti dall'utilizzo o dall'incapacità di utilizzo di questo software. Ciò include, a puro titolo di esempio e senza limitarsi ad essi, la perdita di dati, l'alterazione involontaria o indesiderata di dati, le perdite sostenute da voi o da terze parti o un fallimento del software ad operare con un qualsivoglia altro software. Tale negazione di garanzia rimane in essere anche se i dententori del copyright, o qualsiasi altra parte, è stata avvisata della possibilità di tali danneggiamenti.

Se decidete di utilizzare questo software, lo fate a vostro rischio e pericolo. Se pensate che i termini di questa negazione di garanzia non si confacciano alle vostre esigenze, o al vostro modo di considerare un software, o ancora al modo in cui avete sempre trattato software di terze parti, non usatelo. Se lo usate, accettate espressamente questa negazione di garanzia e la piena responsabilità per qualsiasi tipo di danno, di qualsiasi natura, possa derivarne.

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