在驼鹿默认值中使用localtime

Question

下面的代码有什么问题？运行时,我得到:"在连接(.)中使用未初始化的值或在./main.pl第14行使用字符串"

#!/usr/bin/perl

package Test;

use Moose;

has 'message'     => (isa => 'HashRef', is => 'ro', default => sub{{(localtime)[2] => {(localtime)[3] => "hello"}}});

# the one below works fine
#has 'message'     => (isa => 'HashRef', is => 'ro', default => sub{{"18" => {"16" => "hello"}}});

sub show {
    my $self = shift;
    print("Test: " . $self->message->{(localtime)[2]}->{(localtime)[3]} . "\n");
}

my $o = Test->new();
$o->show();

如果我不使用localtime()那么它工作正常.本地时间[2]和[3]也不会经常变化(2小时,3是月日)所以问题不是那样.如果我用调试器运行脚本,我得到:

x $self
0  Test=HASH(0x3597300)
   'message' => HASH(0x3597618)
      16 => 'hello'

所以看起来我'失去'一级间接,不确定为什么......任何想法？

Answer 1

外部{}不会解析为hashref.添加一个明确的return:

has 'message'     => (isa => 'HashRef', is => 'ro', default => sub{ return {(localtime)[2] => {(localtime)[3] => "hello"}} });

一个+强制这个也有效.

has 'message'     => (isa => 'HashRef', is => 'ro', default => sub{ +{(localtime)[2] => {(localtime)[3] => "hello"}} });