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cluj-pm-2012 - moo

Sat Dec 22 00:30:00 2012

Slides for the talk moo at cluj-pm-2012

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   ______
  < Moo! >
   ~~~~~~
          \   ^__^
           \  (oo)\______
              (__)\             )\/\
                  ||~~~~w |
                  ||           ||

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Moose

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<3

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0.01 released
March 15, 2006

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I started with
about ... 0.18

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0.18 released
March 10, 2007

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What is
Moose?

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What is
Moose
to me?

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The OO I
always knew
perl5 was
capable of

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... but wasn't
good enough
to implement

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Class::Accessor

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Class::Accessor
Class::MakeMethods
Class::Base

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Too many!

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DBIx::Class::AccessorGroup
became
Class::Accessor::Grouped

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Damian
wrote
Class::Std

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... but
nobody
used it

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One class
builder to
rule them all

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Moose

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Why did I
stop using
Moose?

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I didn't.

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Catalyst
is Moose

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All Shadowcat's
clients are
using Moose

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Moose
rocks

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This is all
the Italians'
fault.

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IPW
2009

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Antiquated
Perl

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Web::Simple

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Targets:
usable as CGI

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Targets:
usable as CGI
fast startup
no XS deps

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Wrote my own
accessors

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Wrote my own
constructor

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Perling like
it's 1999

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*GRUMBLE*

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Multiple
projects
like this

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Web::Simple
Data::Query
HTML::Zoom

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Moose use
impedes
adoption

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Mouse?

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Can be
pure perl

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Describes
itself as
"Moose minus
the antlers"

-

Well ...

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It still
has a
metamodel

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The antlers
are just
smaller

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Mouse is
Moose--

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Not what
I wanted

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So I put
on the
hair shirt

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Used no object
system at all
in my projects
for a year

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IT
HURT

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No method
modifiers

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  before foo => sub {
    shift->do_before_foo;
  };

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  sub foo {
    my $self = shift;
    $self->do_before_foo;
    $self->next::method(@_);
  }

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  after foo => sub {
    shift->do_after_foo;
  };

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  sub foo {
    my $self = shift;
    my @ret = wantarray
      ? $self->next::method(@_)
      : scalar $self->next::method(@_)
    $self->do_after_foo;
    return wantarray
      ? @ret
      : $ret[0];
  }

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(and that fails
for void context)

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Intelligent
accessors

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  has foo => (
    is => 'ro',
    lazy => 1,
    builder => '_build_foo'
  );

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  sub foo {
    my $self = shift;
    die "Readonly" in @_;
    unless (exists $self->{foo}) {
      $self->{foo} = $self->_build_foo;
    }
    return $self->{foo}
  }

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Intelligent
constructors

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  has foo => (is => 'ro', required => 1);
  has bar => (is => 'ro', default => sub { 0 });

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  sub new {
    my $class = shift;
    my %args = @_ == 1 ? %{$_[0]} : @_;
    die "foo is required"
      unless exists $args{foo};
    $args{bar} = 0
      unless $args{bar};
    my %new;
    @new{qw(foo bar)} = @args{qw(foo bar)};
    bless (\%new, $class);
  }

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Subclassing
gets even
worse ...

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Runtime
role
application

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  apply_all_roles($obj, @roles)

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  my $new_class = ref($obj).'::__ANON__'.++$i;
  @{"${new_class}::ISA"} = ref($obj);
  eval "package ${new_class}; use $_" for @roles;
  bless($obj, $new_class);

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ARGH

-

-

So ...

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About one
year ago

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Working on
site in
New York

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Bored at the
weekend

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(I am useless
at being
a tourist)

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Coffee.
Subway.

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I hacked.
ribasushi
and frew
tested.

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So, what did
we produce?

-

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Metaprotocol
only needed
for introspection

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Accessor
generation

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Method::Generate::Accessor

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  sub _generate_simple_get {
    my ($self, $me, $name) = @_;
    my $name_str = perlstring $name;
    "${me}->{${name_str}}";
  }

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  sub _generate_get {
    my ($self, $name, $spec) = @_;
    my $simple = $self->_generate_simple_get('$_[0]', $name);
    if ($self->is_simple_get($name, $spec)) {
      $simple;
    } else {
      'do { '.$self->_generate_use_default(
        '$_[0]', $name, $spec,
        $self->_generate_simple_has('$_[0]', $name),
      ).'; '.$simple.' }';
    }
  }

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  has foo => (
    is => 'ro', lazy => 1,
    default => sub { 0 }
  );

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  sub Class::foo {
    do {
      $_[0]->{"foo"} = $default_for_foo->($_[0])
        unless exists $_[0]->{"foo"}; $_[0]->{"foo"}
    }
  }

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Hmm ...

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Why call a sub
if you don't
need to?

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Sub::Quote

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  has foo => (
    is => 'ro', lazy => 1,
    default => quote_sub(q{ 0 })
  );

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  sub Class::foo {
    do {
      $_[0]->{"foo"} = do { @_ = ($_[0]);  0  }
        unless exists $_[0]->{"foo"}; $_[0]->{"foo"}
    }
  }

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Method::Generate::Constructor

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  sub Class::new {
    my $class = shift;
    my $args = @_ == 1 ? %{$_[0]} : {@_};
    my $new = bless({}, $class);
    if (exists $args->{"foo"}) {
      $new->{"foo"} = $args->{"foo"};
    }
    return $new;
  }

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  # generated by the *accessor*
  # system to avoid repeating
  $new->{"foo"} = 

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BUILDALL

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  $new->Super1::BUILD($args);
  $new->Super2::BUILD($args);
  return $new;

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Not quite
that simple

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Subclass may
need a new
constructor

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  package Something;
  use base qw(MooThing);
  sub BUILD { ... }

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  sub MooThing::new {
    my $class = shift;
    if ($class ne "MooThing") {
      Moo->_constructor_maker_for($class,"Class");
      return $class->new(@_);
    }

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Everything
eval()-ed
on demand

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Simple
sugar

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Moose has
lazy_build

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  has foo => (
    is => 'ro',
    lazy => 1,
    builder => '_build_foo',
    predicate => 'has_foo',
    clearer => 'clear_foo'
  );

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Bit too
much.

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  has foo => (
    is => 'ro',
    lazy => 1,
    builder => '_build_foo'
  );

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  has foo => (
    is => 'lazy'
  );

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Now available in Moose via
MooseX::AttributeShortcuts

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Method
Modifiers

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Class::Method::Modifiers

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Moo::import
does -

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  foreach my $type (qw(before after around)) {
    *{_getglob "${target}::${type}"} = sub {
      require Class::Method::Modifiers;
      _install_modifier($target, $type, @_);
    };
  }

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  # avoid upsetting strict
  sub _getglob { \*{$_[0]} }

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Moo::Role

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  foreach my $type (qw(before after around)) {
    *{_getglob "${target}::${type}"} = sub {
      require Class::Method::Modifiers;
      push @{$INFO{$target}{modifiers}||=[]}, [ $type => @_ ];
    };
  }

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Then during
application

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  foreach my $modifier (@{$modifiers||[]}) {
    Class::Method::Modifiers::install_modifier(
      $to, @$modifiers
    );
  }

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Types?

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No type
system

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Lots of
arguing
about
Moose's

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  has foo => (
    ...
    isa => sub {
      <pass check>
        or die "Not a valid thing"
    }
  );

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MooX::Types::MooseLike

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Other
differences?

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Moose:
  use strict;
  use warnings;

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Moo:
  use strictures 1;

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strictures?

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  use strict;
  use warnings FATAL => 'all';

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when run
from a
test ...

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  use strict;
  use warnings FATAL => 'all';
  no indirect;
  no multidimensional;
  no bareword::filehandles;

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Defaults designed
to save newbies
from themselves

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Runtime role
application

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Moose creates
a new class,
applies each
role to it

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Cachable only
per combination
of roles

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Moo ... is
slightly
more clever

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Moo ... is
slightly
more evil

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Creates a
composable
form of
the class

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  before foo => sub {
    $_[0]->do_before_foo
  };

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  sub foo {
    my $self = shift;
    $self->do_before_foo;
    $self->next::method(@_);
  }

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next::method
uses
Class::C3
(or C3 mro
on 5.10+)

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  @{"${new_class}::ISA"} = qw(
    Composed::Role1
    Composed::Role2
    SuperClass
  );

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Done.

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So, total
results?

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  use Moo;
  use Moo::Role;

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extends
has
with
before
after
around

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Quite sufficient
for small projects

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Web::Simple
now uses Moo

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Data::Query
now uses Moo

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DBIx::Class (!)
now uses Moo

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DBIx::Class (!)
now uses Moo
(for the odd
thing it used
to use Moose for)

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  perl -Moo -e 'has ...'
  # like perl -Moose

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13 modules

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~2000 lines
of code and
documentation

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Needs only:
  strictures
  Class::Method::Modifiers

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Needs only:
  strictures
  Class::Method::Modifiers
  Test::More
  Test::Fatal

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Needs only:
  strictures
  Class::Method::Modifiers
  Test::More
  Test::Fatal
  MRO::Compat

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It works.

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It works.
Try it.

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It works.
Try it.
Complain on
#web-simple

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'Moo' is
60% of
'Moose'

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Moo: "almost
but not quite
two thirds
of Moose"

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Questions?

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Thank You
IRC:mst
mst@shadowcat.co.uk
@shadowcat_mst