在Perl中扩展Class:：Accessor以设置父类中的某些属性

我有一个用Class:：Accessor定义的类，如下所示：

package Worker;
use Class::Accessor 'antlers';

# PROPS
has first_name      => ( is => 'rw' );
has position        => ( is => 'rw' );

# METHODS
sub print {
    my $self = shift;

    print "------------\n";
    print "Ref: ", ref $self, "\n";
    print "First Name: ", $self->first_name, "\n";

    if ($self->position) {
        print "Position: ", $self->position, "\n";
    }
}

1;

use Data::Dumper;
use strict;

# Relative Path to Class libraries
use FindBin;
use lib "$FindBin::Bin/.";

use Worker;
use Engineer;

my $wor = Worker->new({first_name => 'Matt'});
my $eng = Engineer->new({first_name => 'Ray'});
$wor->print;
$eng->print;

现在我想创建一个Engineer类，它以这样一种方式扩展Worker，即属性总是设置为：

position=>“Engineer”

例如：

package Engineer;
use Class::Accessor 'antlers';
use Worker;

extends(qw/Worker/);

# METHOS

sub new {
    return bless(__PACKAGE__->SUPER::new({position => 'Engineer'}));
}

1;

但这不起作用，因为当我像这样实例化Engineer类时：

package Worker;
use Class::Accessor 'antlers';

# PROPS
has first_name      => ( is => 'rw' );
has position        => ( is => 'rw' );

# METHODS
sub print {
    my $self = shift;

    print "------------\n";
    print "Ref: ", ref $self, "\n";
    print "First Name: ", $self->first_name, "\n";

    if ($self->position) {
        print "Position: ", $self->position, "\n";
    }
}

1;

use Data::Dumper;
use strict;

# Relative Path to Class libraries
use FindBin;
use lib "$FindBin::Bin/.";

use Worker;
use Engineer;

my $wor = Worker->new({first_name => 'Matt'});
my $eng = Engineer->new({first_name => 'Ray'});
$wor->print;
$eng->print;

我失去了扩展类工程师的第一个名字：

------------
Ref: Worker
First Name: Matt
------------
Ref: Engineer
First Name: 
Position: Engineer

另一方面，我不确定重写返回bless的Engineer->new（）方法是否是个好主意

---

那么，我应该如何使用class:：Accessor扩展Worker类以获得工程师类呢？

这个新的覆盖似乎工作得很好：

package Engineer;
use Class::Accessor 'antlers';
use Worker;
use Data::Dumper;

extends(qw/Worker/);

# METHODS

sub new {
    my($class) = shift;
    my $obj = __PACKAGE__->SUPER::new(@_);
    $obj->position('engineer');
    return bless $obj, $class;
}

setter和getter仍然适用于所有字段，并且在实例化对象时初始化“position”字段