NAME
    Sub::HandlesVia - alternative handles_via implementation

SYNOPSIS
     package Kitchen {
       use Moo;
       use Sub::HandlesVia;
       use Types::Standard qw( ArrayRef Str );
   
       has food => (
         is          => 'ro',
         isa         => ArrayRef[Str],
         handles_via => 'Array',
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

     my $kitchen = Kitchen->new;
     $kitchen->add_food('Bacon');
     $kitchen->add_food('Eggs');
     $kitchen->add_food('Sausages');
     $kitchen->add_food('Beans');
 
     my @foods = $kitchen->find_food(sub { /^B/i });

DESCRIPTION
    If you've used Moose's native attribute traits, or MooX::HandlesVia
    before, you should have a fairly good idea what this does.

    Why re-invent the wheel? Well, this is an implementation that should work
    okay with Moo, Moose, Mouse, and any other OO toolkit you throw at it. One
    ring to rule them all, so to speak.

    Also, unlike MooX::HandlesVia, it honours type constraints, plus it
    doesn't have the limitation that it can't mutate non-reference values.

  Using with Moo
    You should be able to use it as a drop-in replacement for
    MooX::HandlesVia.

     package Kitchen {
       use Moo;
       use Sub::HandlesVia;
       use Types::Standard qw( ArrayRef Str );
   
       has food => (
         is          => 'ro',
         isa         => ArrayRef[Str],
         handles_via => 'Array',
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

  Using with Mouse
    It works the same as Moo basically.

     package Kitchen {
       use Mouse;
       use Sub::HandlesVia;
       use Types::Standard qw( ArrayRef Str );
   
       has food => (
         is          => 'ro',
         isa         => ArrayRef[Str],
         handles_via => 'Array',
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    You are not forced to use Types::Standard. Mouse native types should work
    fine.

     package Kitchen {
       use Mouse;
       use Sub::HandlesVia;
   
       has food => (
         is          => 'ro',
         isa         => 'ArrayRef[Str]',
         handles_via => 'Array',
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    Sub::HandlesVia will also recognize MooseX::NativeTraits-style traits. It
    will jump in and handle them before MooseX::NativeTraits notices!

     package Kitchen {
       use Mouse;
       use Sub::HandlesVia;
   
       has food => (
         is          => 'ro',
         isa         => 'ArrayRef[Str]',
         traits      => ['Array'],
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    (If you have a mouse in your kitchen though, that might not be very
    hygienic.)

  Using with Moose
    It works the same as Mouse basically.

     package Kitchen {
       use Moose;
       use Sub::HandlesVia;
       use Types::Standard qw( ArrayRef Str );
   
       has food => (
         is          => 'ro',
         isa         => ArrayRef[Str],
         handles_via => 'Array',
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    You are not forced to use Types::Standard. Moose native types should work
    fine.

     package Kitchen {
       use Moose;
       use Sub::HandlesVia;
   
       has food => (
         is          => 'ro',
         isa         => 'ArrayRef[Str]',
         handles_via => 'Array',
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    Sub::HandlesVia will also recognize native-traits-style traits. It will
    jump in and handle them before Moose notices!

     package Kitchen {
       use Moose;
       use Sub::HandlesVia;
   
       has food => (
         is          => 'ro',
         isa         => 'ArrayRef[Str]',
         traits      => ['Array'],
         default     => sub { [] },
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    (If you have a moose in your kitchen, that might be even worse than the
    mouse.)

  Using with Anything
    For Moose and Mouse, Sub::HandlesVia can use their metaobject protocols to
    grab an attribute's definition and install the methods it needs to. For
    Moo, it can wrap `has` and do its stuff that way. For other classes, you
    need to be more explicit and tell it what methods to delegate to what
    attributes.

     package Kitchen {
       use Class::Tiny {
         food => sub { [] },
       };
   
       use Sub::HandlesVia qw( delegations );
   
       delegations(
         attribute   => 'food'
         handles_via => 'Array',
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
         },
       );
     }

    Setting `attribute` to "food" means that when Sub::HandlesVia needs to get
    the food list, it will call `$kitchen->food` and when it needs to set the
    food list, it will call `$kitchen->food($value)`. If you have separate
    getter and setter methods, just do:

         attribute   => [ 'get_food', 'set_food' ],

    Or if you don't have any accessors and want Sub::HandlesVia to directly
    access the underlying hashref:

         attribute   => '{food}',

    Or maybe you have a setter, but want to use hashref access for the getter:

         attribute   => [ '{food}', 'set_food' ],

    Or maybe you still want direct access for the getter, but your object is a
    blessed arrayref instead of a blessed hashref:

         attribute   => [ '[7]', 'set_food' ],

    Or maybe your needs are crazy unique:

         attribute   => [ \&getter, \&setter ],

    The coderefs are passed the instance as their first argument, and the
    setter is also passed a value to set.

    Really, I don't think there's any object system that this won't work for!

  What methods can be delegated to?
    The following table compares Sub::HandlesVia with Data::Perl, Moose native
    traits, and MouseX::NativeTraits. Mouse looks like it's ahead of the rest,
    but quite a few of their extra methods are just aliases for existing
    methods.

      Array ===========================================
                accessor : SubHV  DataP  Moose  Mouse
                     all : SubHV  DataP              
                     any :                      Mouse
                   apply :                      Mouse
                   clear : SubHV  DataP  Moose  Mouse
                   count : SubHV  DataP  Moose  Mouse
                  delete : SubHV  DataP  Moose  Mouse
                elements : SubHV  DataP  Moose  Mouse
                   fetch :                      Mouse
                   first : SubHV  DataP  Moose  Mouse
             first_index : SubHV  DataP  Moose       
                 flatten : SubHV  DataP              
            flatten_deep : SubHV  DataP              
                for_each :                      Mouse
           for_each_pair :                      Mouse
                     get : SubHV  DataP  Moose  Mouse
                    grep : SubHV  DataP  Moose  Mouse
                  insert : SubHV  DataP  Moose  Mouse
                is_empty : SubHV  DataP  Moose  Mouse
                    join : SubHV  DataP  Moose  Mouse
                     map : SubHV  DataP  Moose  Mouse
                natatime : SubHV  DataP  Moose       
                     pop : SubHV  DataP  Moose  Mouse
                   print : SubHV  DataP              
                    push : SubHV  DataP  Moose  Mouse
                  reduce : SubHV  DataP  Moose  Mouse
                  remove :                      Mouse
                 reverse : SubHV  DataP              
                     set : SubHV  DataP  Moose  Mouse
           shallow_clone : SubHV  DataP  Moose       
                   shift : SubHV  DataP  Moose  Mouse
                 shuffle : SubHV  DataP  Moose  Mouse
        shuffle_in_place : SubHV                     
                    sort : SubHV  DataP  Moose  Mouse
                 sort_by :                      Mouse
           sort_in_place : SubHV  DataP  Moose  Mouse
        sort_in_place_by :                      Mouse
                  splice : SubHV  DataP  Moose  Mouse
                   store :                      Mouse
                    uniq : SubHV  DataP  Moose  Mouse
           uniq_in_place : SubHV                     
                 unshift : SubHV  DataP  Moose  Mouse

      Bool ============================================
                     not : SubHV  DataP  Moose  Mouse
                   reset : SubHV                     
                     set : SubHV  DataP  Moose  Mouse
                  toggle : SubHV  DataP  Moose  Mouse
                   unset : SubHV  DataP  Moose  Mouse

      Code ============================================
                 execute : SubHV  DataP  Moose  Mouse
          execute_method : SubHV         Moose  Mouse

      Counter =========================================
                     dec : SubHV  DataP  Moose  Mouse
                     inc : SubHV  DataP  Moose  Mouse
                   reset : SubHV  DataP  Moose  Mouse
                     set : SubHV         Moose  Mouse

      Hash ============================================
                accessor : SubHV  DataP  Moose  Mouse
                     all : SubHV  DataP              
                   clear : SubHV  DataP  Moose  Mouse
                   count : SubHV  DataP  Moose  Mouse
                 defined : SubHV  DataP  Moose  Mouse
                  delete : SubHV  DataP  Moose  Mouse
                elements : SubHV  DataP  Moose  Mouse
                  exists : SubHV  DataP  Moose  Mouse
                   fetch :                      Mouse
            for_each_key :                      Mouse
           for_each_pair :                      Mouse
          for_each_value :                      Mouse
                     get : SubHV  DataP  Moose  Mouse
                is_empty : SubHV  DataP  Moose  Mouse
                    keys : SubHV  DataP  Moose  Mouse
                      kv : SubHV  DataP  Moose  Mouse
                     set : SubHV  DataP  Moose  Mouse
           shallow_clone : SubHV  DataP  Moose       
             sorted_keys : SubHV                Mouse
                   store :                      Mouse
                  values : SubHV  DataP  Moose  Mouse

      Number ==========================================
                     abs : SubHV  DataP  Moose  Mouse
                     add : SubHV  DataP  Moose  Mouse
                     div : SubHV  DataP  Moose  Mouse
                     get : SubHV                     
                     mod : SubHV  DataP  Moose  Mouse
                     mul : SubHV  DataP  Moose  Mouse
                     set : SubHV         Moose       
                     sub : SubHV  DataP  Moose  Mouse

      String ==========================================
                  append : SubHV  DataP  Moose  Mouse
                   chomp : SubHV  DataP  Moose  Mouse
                    chop : SubHV  DataP  Moose  Mouse
                   clear : SubHV  DataP  Moose  Mouse
                     get : SubHV                     
                     inc : SubHV  DataP  Moose  Mouse
                  length : SubHV  DataP  Moose  Mouse
                   match : SubHV  DataP  Moose  Mouse
                 prepend : SubHV  DataP  Moose  Mouse
                 replace : SubHV  DataP  Moose  Mouse
        replace_globally : SubHV                Mouse
                   reset : SubHV                     
                     set : SubHV                     
                  substr : SubHV  DataP  Moose  Mouse

  Method Chaining
    Say you have the following

         handles_via => 'Array',
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
           'remove_food' => 'pop',
         },

    Now `$kitchen->remove_food` will remove the last food on the list and
    return it. But what if we don't care about what food was removed? We just
    want to remove the food and discard it. You can do this:

         handles_via => 'Array',
         handles     => {
           'add_food'    => 'push',
           'find_food'   => 'grep',
           'remove_food' => 'pop...',
         },

    Now the `remove_food` method will return the kitchen object instead of
    returning the food. This makes it suitable for chaining method calls:

      # remove the three most recent foods
      $kitchen->remove_food->remove_food->remove_food;

  Hand Waving
    Sub::HandlesVia tries to be strict by default, but you can tell it to be
    less rigourous checking method arguments, etc using the `~` prefix:

         handles_via => 'Array',
         handles     => {
           'find_food'   => '~grep',
         },

  CodeRefs
    You can delegate to coderefs:

         handles_via => 'Array',
         handles    => {
           'find_healthiest' => sub { my $foods = shift; ... },
         }

  Named Methods
    Let's say "FoodList" is a class where instances are blessed arrayrefs of
    strings.

         isa         => InstanceOf['FoodList'],
         handles_via => 'Array',
         handles     => {
           'find_food'             => 'grep',
           'find_healthiest_food'  => 'find_healthiest',
         },

    Now `$kitchen->find_food($coderef)` does this (which breaks encapsulation
    of course):

      my @result = grep $coderef->(), @{ $kitchen->food };

    And `$kitchen->find_healthiest_food` does this:

      $kitchen->food->find_healthiest

    Basically, because `find_healthiest` isn't one of the methods offered by
    Sub::HandlesVia::HandlerList::Array, it assumes you want to call it on the
    arrayref like a proper method.

  Currying Favour
    All this talk of food is making me hungry, but as much as I'd like to eat
    a curry right now, that's not the kind of currying we're talking about.

         handles_via => 'Array',
         handles     => {
           'get_food'   => 'get',
         },

    `$kitchen->get_food(0)` will return the first item on the list.
    `$kitchen->get_food(1)` will return the second item on the list. And so
    on.

         handles_via => 'Array',
         handles     => {
           'first_food'   => [ 'get' => 0 ],
           'second_food'  => [ 'get' => 1 ],
         },

    I think you already know what this does. Right?

    And yes, currying works with coderefs.

         handles_via => 'Array',
         handles     => {
           'blargy'       => [ sub { ... }, @curried ],
         },

  Pick and Mix
        isa         => ArrayRef|HashRef,
        handles_via => [ 'Array', 'Hash' ],
        handles     => {
          the_keys     => 'keys',
          ship_shape   => 'sort_in_place',
        }

    Here you have an attribute which might be an arrayref or a hashref. When
    it's an arrayref, `$object->ship_shape` will work nicely, but
    `$object->the_keys` will fail badly.

    Still, this sort of thing can kind of make sense if you have an object
    that overloads both `@{}` and `%{}`.

    Sometime a method will be ambiguous. For example, there's a `get` method
    for both hashes and arrays. In this case, the array one will win because
    you listed it first in `handles_via`.

    But you can be specific:

        isa         => ArrayRef|HashRef,
        handles_via => [ 'Array', 'Hash' ],
        handles     => {
          get_foo => 'Array->get',
          get_bar => 'Hash->get',
        }

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

    (There are known bugs for Moose native types that do coercion.)

SEE ALSO
    Moose, MouseX::NativeTraits, Data::Perl, MooX::HandlesVia.

AUTHOR
    Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE
    This software is copyright (c) 2020 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.

