如何在Perl Moose中更新哈希属性，更新其他哈希属性

问题描述

此处的hash2属性取决于hash1。实际上，hash2由hash1驱动。例如，

hash1-> key1 => value1，key2 => value2等。

hash2-> key1 => 6，key2 => 6等。它是长度（从hash1到哈希2的值）。

尝试了以下类似方法，但没有帮助。

has 'hash1' => (
    is        => 'rw',isa       => 'HashRef[Str]',default   => sub { {} },handles   => {
        map { $_ . '_hash1' => $_ } @hash_delegations
    },);

has 'hash2' => (
    is        => 'rw',isa       => 'HashRef',builder   => '_filter_hash1',handles   => {
        map { $_ . 'hash2' => $_ } @hash_delegations
    },);

sub _filter_hash1 {
    my $self = shift;
    for my $alias ($self->keys_hash1()) {
        return {$alias,length($alias)};
    }
}

Hash1将随着时间的过去而设置，不确定如何确保应如何捕获hash1上的事件以更新hash2中的条目。知道我该如何实现吗？

解决方法

您是否要创建值长度缓存？实际上，length如此之快，您无需对其进行缓存，但这可能只是更复杂的例子的简化示例。我会使用 trigger ，在第一个哈希上加上一个特征来强制通过方法设置值。直接更改哈希值不会触发其他属性的更改。

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{   package My::Object;
    use Moose;

    my @hash_delegations = qw( keys );

    has 'hash1' => (
        is      => 'rw',isa     => 'HashRef[Str]',default => sub { {} },trigger => \&_update_hash2,traits  => ['Hash'],handles => { set_hash1 => 'set' },);

    has 'hash2' => (
        is     => 'ro',writer => '_set_hash2',isa    => 'HashRef',);

    sub _update_hash2 {
        my ($self,$new,$old) = @_;
        $self->_set_hash2({ map { $_ => length $self->hash1->{$_} }
                            keys %{ $self->hash1 }});
    }
}

my $o = 'My::Object'->new(hash1 => {a => 42,b => 'Universe'});
say $o->hash2->{$_} for qw( a b );

$o->set_hash1(c => '0123456789');
say $o->hash2->{c};

$o->hash1->{c} = "";  # Wrong!
say $o->hash2->{c};   # Didn't change :-(

,

这是一个使用带有触发器和方法修饰符的只读散列的示例...

package MyApp;

use Z qw( Dumper );
use Hash::Util qw( unlock_ref_keys lock_ref_keys );

class '::My::Object' => sub {
    my %common = (
        is       => 'rw',isa      => HashRef[Str],trigger  => sub { lock_ref_keys($_[1]) },default  => sub { lock_ref_keys(my $ref = {}); $ref },handles_via => 'Hash',);
    
    has hash1 => (
        %common,handles  => [
            'set_hash1' => 'set','get_hash1' => 'get',],);
    
    has hash2 => (
        %common,isa      => HashRef[Int],handles  => [
            'set_hash2' => 'set','get_hash2' => 'get',);
    
    around set_hash1 => sub {
        my ( $next,$self,$key,$val ) = ( shift,shift,@_ );
        unlock_ref_keys( $self->hash1 );
        unlock_ref_keys( $self->hash2 );
        my $r = $self->$next( @_ );
        $self->set_hash2( $key,length($val) );
        lock_ref_keys( $self->hash1 );
        lock_ref_keys( $self->hash2 );
        return $r;
    };
    
    method BUILD => sub {
        my ( $self,$args ) = @_;
        if ( my $h1 = $args->{hash1} ) {
            $self->set_hash1( $_,length $h1->{$_} ) for keys %$h1;
        }
    };
};

my $obj = 'My::Object'->new(
    hash1 => { foo => 'xyzzy' },);
$obj->set_hash1('bar','quux');

print Dumper($obj);