File::Find::Object::Rule::Extending(3)

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.