Perl Moose 父类与子类一起转换

Question

package Point;
use Moose;

has 'x' => (isa => 'Int', is => 'rw');
has 'y' => (isa => 'Int', is => 'rw');

package Point3D;
use Moose;

extends 'Point';

has 'z' => (isa => 'Int', is => 'rw');

package main;

use Data::Dumper;

my $point1 = Point->new(x => 5, y => 7);
my $point3d = Point3D->new(z => -5);

$point3d = $point1;
print Dumper($point3d);

是否可以将父类转换为 C++ 等子类？在我的例子中， $point3d 现在是一个 Point 而不是 Point3D 包括 Point。

Answer 1

看看Class::MOP documentation on CPAN ，尤其是 clone_object和 rebless_instance方法:

sub to_3d {
  my ($self, %args) = @_;
  return Point3D->meta->rebless_instance(
    $self->meta->clone_object($self),
    %args,
  );
}

然后像下面这样使用它:

my $point_3d = $point->to_3d(z => 7);

这也会照顾到处理新指定的 %args就好像它们是由构造函数传入的一样。例如。在这个构建过程中，构建器、默认值和类型约束都被考虑在内。