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

  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);

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

use strict;
use warnings;

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

our $VERSION   = '1.12';
$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 _attributes {
    my $self = shift;
    $self->{'attributes'} ||= [ $self->associated_metaclass->get_all_attributes ]
}

## method

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

sub _generate_constructor_method_inline {
    my $self = shift;

    my $defaults = [map { $_->default } @{ $self->_attributes }];

    my $close_over = {
        '$defaults' => \$defaults,
    };

    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 = ' . $self->associated_metaclass->inline_create_instance('$class');
    my $idx = 0;
    $source .= ";\n" . (join ";\n" => map {
        $self->_generate_slot_initializer($_, $idx++)
    } @{ $self->_attributes });
    if (Class::MOP::metaclass_is_weak($self->associated_metaclass->name)) {
        $source .= ";\n" . $self->associated_metaclass->_inline_set_mop_slot('$instance', 'Class::MOP::class_of($class)');
    }
    $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 $idx   = shift;

    my $default;
    if ($attr->has_default) {
        $default = $self->_generate_default_value($attr, $idx);
    } elsif( $attr->has_builder ) {
        $default = '$instance->'.$attr->builder;
    }

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

sub _generate_default_value {
    my ($self, $attr, $index) = @_;
    # NOTE:
    # default values can either be CODE refs
    # in which case we need to call them. Or
    # they can be scalars (strings/numbers)
    # in which case we can just deal with them
    # in the code we eval.
    if ($attr->is_default_a_coderef) {
        return '$defaults->[' . $index . ']->($instance)';
    }
    else {
        return '$defaults->[' . $index . ']';
    }
}

1;

__END__