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File::Find::Object::Rule::Extending.3pm

NAME

File::Find::Object::Rule::Extending - the mini-guide to extending File::Find::Object::Rule

SYNOPSIS

     package File::Find::Object::Rule::Random;
 
     use strict;
     use warnings;
 
     # take useful things from File::Find::Object::Rule
     use base 'File::Find::Object::Rule';
 
     # and force our crack into the main namespace
     sub File::Find::Object::Rule::random () {
         my $self = shift()->_force_object;
         $self->exec( sub { rand > 0.5 } );
     }
 
     1;
 
 

DESCRIPTION

File::Find::Object::Rule inherits File::Find::Rule's extensibility. It is now possibile to extend it, using the following conventions.

Declare your package

     package File::Find::Object::Rule::Random;
 
     use strict;
     use warnings;
 
 

Inherit methods from File::Find::Object::Rule

     # take useful things from File::Find::Object::Rule
     use base 'File::Find::Object::Rule';
 
 

Force your madness into the main package

     # and force our crack into the main namespace
     sub File::Find::Object::Rule::random () {
         my $self = shift()->_force_object;
         $self->exec( sub { rand > 0.5 } );
     }
 
 

Yes, we're being very cavalier here and defining things into the main File::Find::Object::Rule namespace. This is due to lack of imaginiation on my part - I simply can't find a way for the functional and oo interface to work without doing this or some kind of inheritance, and inheritance stops you using two File::Find::Object::Rule::Foo modules together.

For this reason try and pick distinct names for your extensions. If this becomes a problem then I may institute a semi-official registry of taken names.

Taking no arguments.

Note the null prototype on random. This is a cheat for the procedural interface to know that your sub takes no arguments, and so allows this to happen:

  find( random => in => '.' );
 
 

If you hadn't declared "random" with a null prototype it would have consumed "in" as a parameter to it, then got all confused as it doesn't know about a '.' rule.

NOTES ABOUT THE CALLBACK

The callback can access the File::Find::Object::Result using "$self->finder->item_obj()".

AUTHOR

Richard Clamp <richardc@unixbeard.net>

COPYRIGHT

Copyright (C) 2002 Richard Clamp. All Rights Reserved.

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

SEE ALSO

File::Find::Object::Rule

File::Find::::Rule::MMagic was the first extension module for File::Find::Rule, so maybe check that out.