NAME

       Kavorka::Manual::ExtendingKavorka - extending Kavorka with traits and new keywords

DESCRIPTION

   Traits
       Many of the code constructs handled by Kavorka allow a list of traits to be given. Subs can have traits:

          method xyz ($x, $y, $z) is friendly { ... }

       So can parameters within signatures:

          method xyz ($x is hot, $y does warm, $z but cool) { ... }

       And return types:

          method get_age (Date $date → Num $age is years) { ... }

       When a trait is used which isn't natively handled by Kavorka::Sub, Kavorka::Parameter or
       Kavorka::ReturnType, Kavorka will attempt to load a Moo::Role to handle the trait. These will be loaded
       from the following namespaces, as appropriate:

       •   "Kavorka::TraitFor::Sub::*"

       •   "Kavorka::TraitFor::Parameter::*"

       •   "Kavorka::TraitFor::ReturnType::*"

       For example, "Kavorka::TraitFor::Sub::friendly".

   Trait Parameters
       Although  none  of  Kavorka's  native  traits  make  use  of this syntax, traits can be followed by trait
       parameters in parentheses:

          BEGIN {
             package Kavorka::TraitFor::Parameter::debug;
             use Moo::Role;
             around injection => sub
             {
                my $next = shift;
                my $self = shift;
                my $code = $self->$next(@_);
                $code .= sprintf(
                   "printf STDERR %s, %s, %s;",
                   B::perlstring($self->traits->{debug}[0]),
                   B::perlstring($self->name),
                   $self->name,
                );
                return $code;
             };
          }

          use Kavorka;

          fun foo ( $x but debug("%s is %s\n") ) {
             ## Injected:
             ## printf STDERR "%s is %s\n", "\$x", $x;
             return $x;
          }

          foo(42);  # says to STDERR: '$x is 42'

   Keywords
       Traits are not applied to subs until after they've been parsed, which  means  that  traits  cannot,  say,
       alter how the signature is parsed, because the signature occurs before the traits.

       For more advanced control over the parsing and behaviour of subs, you would need to create a new keyword.
       A  keyword  is  just  a  Moo  class  which  consumes  the  Kavorka::Sub  role.  Kavorka::Sub::Method  and
       Kavorka::Sub::Fun are simple examples of such keyword classes.

       People can use your new keyword like this:

          use Kavorka yourkeyword => { implementation => "Your::Class" };

BUGS

       Please report any bugs to <http://rt.cpan.org/Dist/Display.html?Queue=Kavorka>.

SEE ALSO

       Kavorka::Manual.

AUTHOR

       Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

       This software is copyright (c) 2013-2014, 2017 by Toby Inkster.

       This is free software; you can redistribute it and/or modify it under  the  same  terms  as  the  Perl  5
       programming language system itself.

DISCLAIMER OF WARRANTIES

       THIS  PACKAGE  IS  PROVIDED  "AS  IS"  AND  WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
       LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

perl v5.28.1                                       2019-01-17             Kavorka::Manual::ExtendingKavorka(3pm)