perl – 使用Hash :: Merge合并数组的哈希值

发布时间：2020-12-15 21:45:57 所属栏目：大数据来源：网络整理

导读：我正在尝试使用 Hash::Merge 合并包含一个或多个数组的两个哈希值.例如： use strict;use warnings;use feature qw(say);use Data::Dump qw(dump);use Hash::Merge qw(merge);my $h1 = { a = [ { aa = 1 },3 ] };my $h2 = { a = [ { bb = 2 } ] };my $hLeft

我正在尝试使用 Hash::Merge合并包含一个或多个数组的两个哈希值.例如：

use strict;
use warnings;
use feature qw(say);

use Data::Dump qw(dump);
use Hash::Merge qw(merge);

my $h1 = { a => [ { aa => 1 },3 ] };
my $h2 = { a => [ { bb => 2 } ] };

my $hLeft  = merge( $h1,$h2 );
my $hRight = merge( $h2,$h1 );

say "  hLeft: " . dump($hLeft);
say " hRight: " . dump($hRight);

my $hDesired = { a => [ { aa => 1,bb => 2 },3 ] };
say "Desired: " . dump($hDesired);

这给出了输出：

hLeft: { a => [{ aa => 1 },3,{ bb => 2 }] }
 hRight: { a => [{ bb => 2 },{ aa => 1 },3] }
Desired: { a => [{ aa => 1,3] }

如何使用Hash :: Merge获得正确的输出？

解决方法

合并数组的默认行为是追加它们：

sub { [ @{$_[0]},@{$_[1]} ] },

要获得不同的行为,必须使用Hash::Merge::specify_behavior.

以下解决方案是LEFT_PRECEDENT,并将数组元素合并到元素：

use strict;
use warnings;
use feature qw(say);

use Data::Dump qw(dump);
use Hash::Merge qw(merge);

Hash::Merge::specify_behavior(
    {   'SCALAR' => {
            'SCALAR' => sub { $_[0] },'ARRAY'  => sub { $_[0] },'HASH'   => sub { $_[0] },},'ARRAY' => {
            'SCALAR' => sub { [ @{ $_[0] },$_[1] ] },'ARRAY'  => sub {
                my ( $left,$right ) = @_;

                my @merged = @$left;
                my @to_add = @$right;

                for (@merged) {
                    last if !@to_add;
                    $_ = Hash::Merge::merge( $_,shift @to_add );
                }

                return [ @merged,@to_add ];
            },'HASH'  => sub { [ @{ $_[0] },values %{ $_[1] } ] },'HASH' => {
            'SCALAR' => sub { $_[0] },'HASH'   => sub { Hash::Merge::_merge_hashes( $_[0],$_[1] ) },'My Behavior',);

my $h1 = { a => [ { aa => 1 },3 ] };
my $h2 = { a => [ { bb => 2 } ] };

my $merged = merge( $h1,$h2 );
say "Merged: " . dump($merged);

输出：

Merged: { a => [{ aa => 1,3] }

（编辑：李大同）

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