Question

出于好奇，还有另一种方法来提取我的AoH结构的子集吗？ AoH是“矩形”（即保证在所有hashref上具有相同的键）。

使用temp var和嵌套map对于基本上是花哨的哈希切片来说似乎有点太多了：

use strict;
use warnings;
use Data::Dump 'dump';

my $AoH = [ # There are many more keys in the real structure

            { a => "0.08", b => "0.10", c => "0.25" },
            { a => "0.67", b => "0.85", c => "0.47" },
            { a => "0.06", b => "0.57", c => "0.84" },
            { a => "0.15", b => "0.67", c => "0.90" },
            { a => "1.00", b => "0.36", c => "0.85" },
            { a => "0.61", b => "0.19", c => "0.70" },
            { a => "0.50", b => "0.27", c => "0.33" },
            { a => "0.06", b => "0.69", c => "0.12" },
            { a => "0.83", b => "0.27", c => "0.15" },
            { a => "0.74", b => "0.25", c => "0.36" },
          ];

# I just want the 'a's and 'b's

my @wantedKeys = qw/ a b /;  # Could have multiple unwanted keys in reality

my $a_b_only = [
                  map { my $row = $_;
                        +{
                           map { $_ => $row->{$_} } @wantedKeys
                         }
                  }
                  @$AoH
               ];

dump $a_b_only; # No 'c's here

Answer 1

如果你不再需要$ AoH，你可以使用破坏性的方式：

delete $_->{c} for @$AoH;

Answer 2

这是一个map和一个任意的键列表：

my @wantedKeys = qw/a b/;
my $wanted = [
    map { my %h; @h{@wantedKeys} = @{ $_ }{@wantedKeys}; \%h }  @$AoH
];

（在this post）的帮助下

Answer 3

您想要delete。

my $foo = [ map { delete $_->{c}; $_  } @$AoH ];

如果要保留原始数据，则需要先取消引用哈希值。

my $foo = [ map { my %hash = %$_; delete $hash{c}; \%hash; } @$AoH ];

Answer 4

这是我的解决方案（让我介绍一下很好的Data :: Printer模块）：

use Modern::Perl;
use Data::Printer { colored => 1 };

my $AoH = [
            { a => "0.08", b => "0.10", c => "0.25" },
            { a => "0.67", b => "0.85", c => "0.47" },
            { a => "0.06", b => "0.57", c => "0.84" },
            { a => "0.15", b => "0.67", c => "0.90" },
            { a => "1.00", b => "0.36", c => "0.85" },
            { a => "0.61", b => "0.19", c => "0.70" },
            { a => "0.50", b => "0.27", c => "0.33" },
            { a => "0.06", b => "0.69", c => "0.12" },
            { a => "0.83", b => "0.27", c => "0.15" },
            { a => "0.74", b => "0.25", c => "0.36" },
          ];

# I just want the 'a's and 'b's, so I build a new hash with the keys I want
my @ab = map { {a=>$_->{a}, b=>$_->{b}} } @$AoH;
p @ab;

# If you don't mind remove the "c" key in your original structure:
#  map { delete $_->{c} } @$AoH;
#  and $AoH is an array of hashes without the "c" key.

这是在Perl中提取AoH子集的最简洁方法吗？

4 个答案: