refactor this to use _eval_environment

[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';
use Try::Tiny;

our $VERSION   = '1.11';
$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 _eval_environment {
    my $self = shift;
    my $defaults = [map { $_->default } @{ $self->_attributes }];
    return {
        '$defaults' => \$defaults,
    };
}

sub _generate_constructor_method_inline {
    my $self = shift;

    my $meta = $self->associated_metaclass;

    my $idx = 0;
    my @source = (
        'sub {',
            'my $class = shift;',
            'return Class::MOP::Class->initialize($class)->new_object(@_)',
                'if $class ne \'' . $meta->name . '\';',
            'my $params = @_ == 1 ? $_[0] : {@_};',
            'my $instance = ' . $meta->inline_create_instance('$class') . ';',
            (map { $self->_generate_slot_initializer($_, $idx++) }
                 @{ $self->_attributes }),
            $self->_preserve_weak_metaclasses,
            'return $instance',
        '}',
    );

    warn join("\n", @source) if $self->options->{debug};

    my $code = try {
        $self->_compile_code(\@source);
    }
    catch {
        my $source = join("\n", @source);
        confess "Could not eval the constructor :\n\n$source\n\nbecause :\n\n$_";
    };

    return $code;
}

sub _generate_slot_initializer {
    my $self  = shift;
    my ($attr, $idx) = @_;

    my $default = $self->_generate_default_value($attr, $idx);

    if (defined(my $init_arg = $attr->init_arg)) {
        my @source = (
            'if (exists $params->{\'' . $init_arg . '\'}) {',
                $attr->inline_set(
                    '$instance', '$params->{\'' . $init_arg . '\'}'
                ) . ';',
            '}',
        );
        if (defined $default) {
            push @source, (
                'else {',
                    $attr->inline_set('$instance', $default) . ';',
                '}',
            );
        }
        return @source;
    }
    elsif (defined $default) {
        return ($attr->inline_set('$instance', $default) . ';');
    }
    else {
        return ();
    }
}

sub _preserve_weak_metaclasses {
    my $self = shift;
    my $meta = $self->associated_metaclass;
    if (Class::MOP::metaclass_is_weak($meta->name)) {
        return (
            $meta->_inline_set_mop_slot(
                '$instance', 'Class::MOP::class_of($class)'
            ) . ';'
        );
    }
    else {
        return ();
    }
}

sub _generate_default_value {
    my $self = shift;
    my ($attr, $index) = @_;

    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) {
            return '$defaults->[' . $index . ']->($instance)';
        }
        else {
            return '$defaults->[' . $index . ']';
        }
    }
    elsif ($attr->has_builder) {
        return '$instance->' . $attr->builder;
    }
    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 2006-2010 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