Implement an idea of reducing inline constructors in basic metaclasses

[gitmo/Class-MOP.git] / lib / Class / MOP / Method / Constructor.pm

package Class::MOP::Method::Constructor;

use strict;
use warnings;

use Carp         'confess';
use Scalar::Util 'blessed', 'weaken', 'looks_like_number';

our $VERSION   = '0.89';
$VERSION = eval $VERSION;
our $AUTHORITY = 'cpan:STEVAN';

use base 'Class::MOP::Method::Inlined';

sub new {
    my $class   = shift;
    my %options = @_;

    (blessed $options{metaclass} && $options{metaclass}->isa('Class::MOP::Class'))
        || confess "You must pass a metaclass instance if you want to inline"
            if $options{is_inline};

    ($options{package_name} && $options{name})
        || confess "You must supply the package_name and name parameters $Class::MOP::Method::UPGRADE_ERROR_TEXT";

    my $self = $class->_new(\%options);

    # we don't want this creating
    # a cycle in the code, if not
    # needed
    weaken($self->{'associated_metaclass'});

    $self->_initialize_body;

    return $self;
}

sub _new {
    my $class = shift;
    return Class::MOP::Class->initialize($class)->new_object(@_)
      if $class ne __PACKAGE__;

    my $params = @_ == 1 ? $_[0] : {@_};

    return bless {
        # inherited from Class::MOP::Method
        body                 => $params->{body},
        # associated_metaclass => $params->{associated_metaclass}, # overriden
        package_name         => $params->{package_name},
        name                 => $params->{name},
        original_method      => $params->{original_method},

        # inherited from Class::MOP::Generated
        is_inline            => $params->{is_inline} || 0,
        definition_context   => $params->{definition_context},

        # inherited from Class::MOP::Inlined
        _expected_method_class => $params->{_expected_method_class},

        # defined in this subclass
        options              => $params->{options} || {},
        associated_metaclass => $params->{metaclass},
    }, $class;
}

## accessors

sub options              { (shift)->{'options'}              }
sub associated_metaclass { (shift)->{'associated_metaclass'} }

## cached values ...

sub meta_instance {
    Carp::cluck('The meta_instance method has been made private.'
        . " The public version is deprecated and will be removed in a future release.\n");
    shift->_meta_instance;
}

sub _meta_instance {
    my $self = shift;
    $self->{'meta_instance'} ||= $self->associated_metaclass->get_meta_instance;
}

sub attributes {
    Carp::cluck('The attributes method has been made private.'
        . " The public version is deprecated and will be removed in a future release.\n");

    return shift->_attributes;
}

sub _attributes {
    my $self = shift;
    $self->{'attributes'} ||= [ $self->associated_metaclass->get_all_attributes ]
}

## method

sub initialize_body {
    Carp::cluck('The initialize_body method has been made private.'
        . " The public version is deprecated and will be removed in a future release.\n");
    shift->_initialize_body;
}

sub _initialize_body {
    my $self        = shift;
    my $method_name = '_generate_constructor_method';

    $method_name .= '_inline' if $self->is_inline;

    $self->{'body'} = $self->$method_name;
}

sub generate_constructor_method {
    Carp::cluck('The generate_constructor_method method has been made private.'
        . " The public version is deprecated and will be removed in a future release.\n");
    shift->_generate_constructor_method;
}

sub _generate_constructor_method {
    return sub { Class::MOP::Class->initialize(shift)->new_object(@_) }
}

sub generate_constructor_method_inline {
    Carp::cluck('The generate_constructor_method_inline method has been made private.'
        . " The public version is deprecated and will be removed in a future release.\n");
    shift->_generate_constructor_method_inline;
}

sub _generate_constructor_method_inline {
    my $self = shift;

    my $close_over = {};

    my $source = 'sub {';
    $source .= "\n" . 'my $class = shift;';

    $source .= "\n" . 'return Class::MOP::Class->initialize($class)->new_object(@_)';
    $source .= "\n" . '    if $class ne \'' . $self->associated_metaclass->name . '\';';

    $source .= "\n" . 'my $params = @_ == 1 ? $_[0] : {@_};';

    $source .= "\n" . 'my $instance = ' . $self->_meta_instance->inline_create_instance('$class');
    $source .= ";\n" . (join ";\n" => map {
        $self->_generate_slot_initializer($_, $close_over)
    } @{ $self->_attributes });
    $source .= ";\n" . 'return $instance';
    $source .= ";\n" . '}';
    warn $source if $self->options->{debug};

    my ( $code, $e ) = $self->_eval_closure(
        $close_over,
        $source
    );
    confess "Could not eval the constructor :\n\n$source\n\nbecause :\n\n$e" if $e;

    return $code;
}

sub _generate_slot_initializer {
    my $self  = shift;
    my $attr  = shift;
    my $close = shift;

    my $default;
    if ($attr->has_default) {
        # NOTE:
        # default values can either be CODE refs
        # in which case we need to call them. Or
        # they can be scalars (strings/numbers)
        # in which case we can just deal with them
        # in the code we eval.
        if ($attr->is_default_a_coderef) {
            my $idx = @{$close->{'@defaults'}||=[]};
            push(@{$close->{'@defaults'}}, $attr->default);
            $default = '$defaults[' . $idx . ']->($instance)';
        }
        else {
            $default = $attr->default;
            # make sure to quote strings ...
            unless (looks_like_number($default)) {
                $default = "'$default'";
            }
        }
    } elsif( $attr->has_builder ) {
        $default = '$instance->'.$attr->builder;
    }

    if ( defined(my $init_arg = $attr->init_arg) ) {
      return (
          'if(exists $params->{\'' . $init_arg . '\'}){' . "\n" .
                $self->_meta_instance->inline_set_slot_value(
                    '$instance',
                    $attr->name,
                    '$params->{\'' . $init_arg . '\'}' ) . "\n" .
           '} ' . (!defined $default ? '' : 'else {' . "\n" .
                $self->_meta_instance->inline_set_slot_value(
                    '$instance',
                    $attr->name,
                     $default ) . "\n" .
           '}')
        );
    } elsif ( defined $default ) {
        return (
            $self->_meta_instance->inline_set_slot_value(
                '$instance',
                $attr->name,
                 $default ) . "\n"
        );
    } else { return '' }
}

1;

__END__

=pod

=head1 NAME

Class::MOP::Method::Constructor - Method Meta Object for constructors

=head1 SYNOPSIS

  use Class::MOP::Method::Constructor;

  my $constructor = Class::MOP::Method::Constructor->new(
      metaclass => $metaclass,
      options   => {
          debug => 1, # this is all for now
      },
  );

  # calling the constructor ...
  $constructor->body->execute($metaclass->name, %params);

=head1 DESCRIPTION

This is a subclass of C<Class::MOP::Method> which generates
constructor methods.

=head1 METHODS

=over 4

=item B<< Class::MOP::Method::Constructor->new(%options) >>

This creates a new constructor object. It accepts a hash reference of
options.

=over 8

=item * metaclass

This should be a L<Class::MOP::Class> object. It is required.

=item * name

The method name (without a package name). This is required.

=item * package_name

The package name for the method. This is required.

=item * is_inline

This indicates whether or not the constructor should be inlined. This
defaults to false.

=back

=item B<< $metamethod->is_inline >>

Returns a boolean indicating whether or not the constructor is
inlined.

=item B<< $metamethod->associated_metaclass >>

This returns the L<Class::MOP::Class> object for the method.

=back

=head1 AUTHORS

Stevan Little E<lt>stevan@iinteractive.comE<gt>

=head1 COPYRIGHT AND LICENSE

Copyright 2006-2009 by Infinity Interactive, Inc.

L<http://www.iinteractive.com>

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

=cut