Question

抱歉有点长的代码，但想提供一个近乎有效的例子。

package MLQ::Jobs::Job {
    use 5.016;
    use Moose;
    use warnings;
    has 'name' => (is=>'rw', isa=>'Str');
    has 'status' => (is=>'rw', isa=>'Str');
}

package MLQ::Jobs {
    use 5.016;
    use Moose;
    use warnings;
    #use MLQ::Jobs::Job;

    has jobs => (
        is => 'rw',
        isa =>'ArrayRef[MLQ::Jobs::Job]',     #jobs - an array of zero to many jobs
        builder => '_scan_jobs',              #initializing it when creating the object Jobs
    );

    sub _scan_jobs {
        my $self = shift;
        #test code
        foreach my $i (1..10) {
            my $j = MLQ::Jobs::Job->new();
            $j->name("name $i");
            $j->status("stat $i");
            push @{$self->{jobs}}, $j;
        }
    }
}

package main {
    use 5.016;
    use warnings;
    use Data::Dumper;
    #use MLQ::Jobs;
    my $j = MLQ::Jobs->new();
    say Dumper $j;
}

运行上述代码时，得到10行长的错误消息什么是不有帮助。至少对一个偶然的perl程序员没有帮助 - 就像我...... :(理解第一行，但在代码中找不到错误...

Attribute (jobs) does not pass the type constraint because: Validation failed for 'ArrayRef[MLQ::Jobs::Job]' with value  at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Moose/Meta/Attribute.pm line 1289.
        Moose::Meta::Attribute::verify_against_type_constraint('Moose::Meta::Attribute=HASH(0x7fce1082ec78)', '', 'instance', 'MLQ::Jobs=HASH(0x7fce1082a378)') called at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Moose/Meta/Attribute.pm line 1276
        Moose::Meta::Attribute::_coerce_and_verify('Moose::Meta::Attribute=HASH(0x7fce1082ec78)', '', 'MLQ::Jobs=HASH(0x7fce1082a378)') called at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Moose/Meta/Attribute.pm line 546
        Moose::Meta::Attribute::initialize_instance_slot('Moose::Meta::Attribute=HASH(0x7fce1082ec78)', 'Moose::Meta::Instance=HASH(0x7fce1082f4a0)', 'MLQ::Jobs=HASH(0x7fce1082a378)', 'HASH(0x7fce1082a360)') called at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Class/MOP/Class.pm line 525
        Class::MOP::Class::_construct_instance('Moose::Meta::Class=HASH(0x7fce108372a8)', 'HASH(0x7fce1082a360)') called at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Class/MOP/Class.pm line 498
        Class::MOP::Class::new_object('Moose::Meta::Class=HASH(0x7fce108372a8)', 'HASH(0x7fce1082a360)') called at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Moose/Meta/Class.pm line 274
        Moose::Meta::Class::new_object('Moose::Meta::Class=HASH(0x7fce108372a8)', 'HASH(0x7fce1082a360)') called at /Users/me/perl5/perlbrew/perls/perl-5.16.3/lib/site_perl/5.16.3/darwin-2level/Moose/Object.pm line 28
        Moose::Object::new('MLQ::Jobs') called at moo2.pl line 38

Answer 1

问题是builder方法（如default）应该返回要放在属性中的值，而不是初始化属性本身。你可以用BUILD方法做到这一点。

sub _scan_jobs {
    my $self = shift;

    my @jobs;
    foreach my $i (1..10) {
        my $j = MLQ::Jobs::Job->new();
        $j->name("name $i");
        $j->status("stat $i");
        push @jobs, $j;
    }

    return \@jobs;
}

如何在Moose中使用ArrayRef [Class]

1 个答案: