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Filename : Extending.pod
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=head1 NAME

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

=head1 SYNOPSIS

 package File::Find::Rule::Random;
 use strict;
 
 # take useful things from File::Find::Rule
 use base 'File::Find::Rule';

 # and force our crack into the main namespace
 sub File::Find::Rule::random () {
     my $self = shift()->_force_object;
     $self->exec( sub { rand > 0.5 } );
 }
 
 1;

=head1 DESCRIPTION

File::Find::Rule went down so well with the buying public that
everyone wanted to add extra features.  With the 0.07 release this
became a possibility, using the following conventions.

=head2 Declare your package

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

=head2 Inherit methods from File::Find::Rule

 # take useful things from File::Find::Rule
 use base 'File::Find::Rule';
 
=head3 Force your madness into the main package

 # and force our crack into the main namespace
 sub File::Find::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::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::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.

=head2 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 C<random> with a null prototype it would have
consumed C<in> as a parameter to it, then got all confused as it
doesn't know about a C<'.'> rule.

=head1 AUTHOR

Richard Clamp <richardc@unixbeard.net>

=head1 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.

=head1 SEE ALSO

L<File::Find::Rule>

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

=cut