Moo处理=>的“角色”不工作

Question

在我的一生中，我无法理解为什么这不像文档所说的那样起作用。我在谷歌上搜索了这个问题，查看了源代码，等等。这是一个错误，还是我做错了什么，我就是看不见。

下面是代码：#！/usr/bin/

use strict;
use warnings;

package Model;

use Moo::Role;

has ObjectID => (
    is => 'rw'
);

package Object;

use Moo; 
use namespace::clean;

has model => (
    is => 'rw',
    handles => 'Model'
);

package main;

my $xo = Object->new;
$xo->ObjectID(12345);

exit;

试图跑

perl -MCarp::Always t/moohandles.t

拿着这个

Attempted to access 'model' but it is not set at (eval 26) line 20.
    Object::_assert_model('Object=HASH(0x1dfd118)') called at (eval 25) line 17
    Object::ObjectID('Object=HASH(0x1dfd118)', 12345) called at t/moohandles.t line 27

Answer 1

委托实际上扩展了$xo->ObjectID方法对$xo->model->ObjectID的调用。但$xo->model目前尚未设置。您可能希望将其默认为消耗Model角色的对象。

就像这样：

use strict;
use warnings;

{
  package Model;
  use Moo::Role;
  has ObjectID => (
    is => 'rw',
  );
}

{
  package ModelClass;
  use Moo;
  with 'Model';
}

{
  package Object;
  use Moo;
  has model => (
    is => 'rw',
    handles => 'Model',
    builder => sub { ModelClass->new },
  );
}

my $xo = Object->new;
$xo->ObjectID(12345);
print $xo->ObjectID, "\n";