PROSAGA码农传奇-perl-Moo对象扩展顺序

<div class =“post-text”itemprop =“text”>
  <P>
    由于您对相关数组进行了变异，因此您不希望引用您用作默认数组的数组
     <code>
      \@list
    </code>
    ，你想要一个浅的副本
     <code>
      [@list]
    </code>
    。
  </p>
   <pre>
    <code>
      package t;

use Moo;
use Types::Standard qw(ArrayRef);

my @list = qw/foo bar baz/;

has list => (
    is => 'rw',
    isa => ArrayRef,
        builder =>
    default => sub { [@list] }
);

package u;

use Moo;
use Types::Standard qw(ArrayRef);
extends 't';

sub BUILD {
    my ($self) = @_;

push @{$self->list()}, qw/apple banana/;
    return $self;
}

package main;

use Data::Printer;

my $u = u->new();
p $u->list();

my $t = t->new();
p $t->list();

</code>
  </pre>
  <HR />
  <P>
    虽然我在这里，但使用BUILD来修改属性是可能的，但不一定是最好的。你可以使用一个类似于惰性属性的东西和一个构建器方法，然后在子类ala中重载该方法
  </p>
   <pre>
    <code>
      package t;

use Moo;
use Types::Standard qw(ArrayRef);

my @list = qw/foo bar baz/;

has list => (
    is => 'rw',
    isa => ArrayRef,
    builder => '_build_list',
    lazy => 1,
);

sub _build_list {
  my $self = shift;
  return [@list];
}

package u;

use Moo;
extends 't';

sub _build_list {
  my $self = shift;
  my $list = $self->SUPER::_build_list();
  push @$list, qw/apple banana/;
  return $list;
}

package main;

use Data::Printer;

my $u = u->new();
p $u->list();

my $t = t->new();
p $t->list();

</code>
  </pre>
</DIV>