如何在 Moose 属性编写器中合并 HashRef？

Question

有一个简单的示例代码

use Modern::Perl;
use Data::Dumper;

package My;
use Moose;
use Method::Signatures::Simple;
has 'result' => (
    is => 'rw',
    isa => 'HashRef',
    default => sub{{}},
    clearer => 'clear_result'
);

method run {
    $self->clear_result;                 #clearing the result
    $self->result( $self->run_part1 );
    $self->do_something;
    $self->result( $self->run_part3 );   #need merge
}

method do_something {
    $self->result( $self->run_part2 );   #need merge
}

method run_part1 { return { aaa => 'aaa' } }
method run_part2 { return { bbb => 'bbb' } }
method run_part3 { return { ccc => 'ccc' } }

package main;
my $p = My->new;
say Dumper $p->run;

结果（当然）是：

$VAR1 = {
          'ccc' => 'ccc'
        };

我想要结果：

$VAR1 = {
          'aaa' => 'aaa'
          'bbb' => 'bbb'
          'ccc' => 'ccc'
        };

那么，问题是——设置时如何合并$self->resultHashRef？

是的，我可以添加新方法add_result，例如：

method add_result($hr) {
    use Hash::Merge::Simple qw(merge);
    $self->result( merge $self->result, $hr );
}

并且在我的代码中将$self->result 更改为$self->add_result，但想知道是否还有其他解决方案...

Answer 1

has 'result' => (
    acccessor => '_result',
    isa => 'HashRef',
    default => sub{{}},
    clearer => 'clear_result'
);

sub result {
    my $self = shift;
    if (@_) {
        my ($hr) = @_;
        return $self->_result( ... merged hash ...);
    } else {
        return $self->_result();
    }   
}