Perl WWW：机械化访问散列引用中的数据

我有一个问题，希望你能帮我？

这是我在理解散列引用时需要帮助的最后一部分

代码：

my $content_lengths; # this is at the top
foreach my $url ( # ... more stuff

# compare
if ( $mech->response->header('Content-Length') != $content_length ) {
  print "$child_url: different content length: $content_length vs "
    . $mech->response->header('Content-Length') . "!\n";

  # store the urls that are found to have different content
  # lengths to the base url only if the same url has not already been stored
  $content_lengths->{$url}->{'different'}->{$child_url} = $mech->response->header('Content-Length');

} elsif ( $mech->response->header('Content-Length') == $content_length ) {
  print "Content lengths are the same\n";

  # store the urls that are found to have the same content length as the base
  # url only if the same url has not already been stored
  $content_lengths->{$url}->{'equal'}->{$child_url} = $mech->response->header('Content-Length');
}

使用Data:：Dumper时的样子

$VAR1 = {
      'http://www.superuser.com/' => {
                                       'difference' => {
                                                         'http://www.superuser.com/questions' => '10735',
                                                         'http://www.superuser.com/faq' => '13095'
                                                       },
                                       'equal' => {
                                                    'http://www.superuser.com/ ' => '20892'
                                                  }
                                     },
      'http://www.stackoverflow.com/' => {
                                           'difference' => {
                                                             'http://www.stackoverflow.com/faq' => '13015',
                                                             'http://www.stackoverflow.com/questions' => '10506'
                                                           },
                                           'equal' => {
                                                        'http://www.stackoverflow.com/ ' => '33362'
                                                      }
                                         }
    };

我需要什么帮助：

my $content_lengths; # this is at the top
foreach my $url ( # ... more stuff

# compare
if ( $mech->response->header('Content-Length') != $content_length ) {
  print "$child_url: different content length: $content_length vs "
    . $mech->response->header('Content-Length') . "!\n";

  # store the urls that are found to have different content
  # lengths to the base url only if the same url has not already been stored
  $content_lengths->{$url}->{'different'}->{$child_url} = $mech->response->header('Content-Length');

} elsif ( $mech->response->header('Content-Length') == $content_length ) {
  print "Content lengths are the same\n";

  # store the urls that are found to have the same content length as the base
  # url only if the same url has not already been stored
  $content_lengths->{$url}->{'equal'}->{$child_url} = $mech->response->header('Content-Length');
}

我需要帮助理解访问散列引用中不同部分的各种方法，并使用它们来做一些事情，例如打印它们

例如，我如何从散列引用（即，从将要使用和的Data:：Dumper）打印所有

$url

如何打印

$child\u url

中的全部或

$child\u url

中的特定一个/子集，依此类推

非常感谢您的帮助，

---

非常感谢

您可以浏览您的hashref，从而：

$hashref->{key1}{key2}{keyN};

例如，如果希望超级用户相等分支：

my $urlArrayref = $hashref->{'http://www.superuser.com/'}{'equal'};

更重要的是，要打印hashref的URL（第一级键），您需要执行以下操作：

foreach my $key ( keys( %{$hashref} ) ) {
    print( "key is '$key'\n" );
}

然后，如果需要第二级关键点：

foreach my $firstLevelKey ( keys( %{$hashref} ) ) {
    print( "first level key is '$firstLevelKey'\n" );
    foreach my $secondLevelKey ( keys( %{$hashref->{$firstLevelKey}} ) ) {
        print( "\tfirst level key is '$secondLevelKey'\n" );
    }
}

等等

----编辑---

这是上面示例中的工作示例代码：

#!/usr/bin/perl

use strict;
use warnings;

my $content_lengths = {
    'http://www.superuser.com/' => {
        'difference' => {
            'http://www.superuser.com/questions' => '10735',
            'http://www.superuser.com/faq' => '13095'
        },
        'equal' => {
            'http://www.superuser.com/ ' => '20892'
        }
    },
    'http://www.stackoverflow.com/' => {
        'difference' => {
            'http://www.stackoverflow.com/faq' => '13015',
            'http://www.stackoverflow.com/questions' => '10506'
        },
        'equal' => {
            'http://www.stackoverflow.com/ ' => '33362'
        }
    }
};

foreach my $key1 ( keys( %{$content_lengths} ) ) {
    print( "$key1\n" );
    foreach my $key2 ( keys( %{$content_lengths->{$key1}} ) ) {
        print( "\t$key2\n" );
        foreach my $key3 ( keys( %{$content_lengths->{$key1}{$key2}} ) ) {
            print( "\t\t$key3\n" );
        }
    }
}

这将导致此输出：

http://www.superuser.com/
        difference
                http://www.superuser.com/questions
                http://www.superuser.com/faq
        equal
                http://www.superuser.com/
http://www.stackoverflow.com/
        difference
                http://www.stackoverflow.com/faq
                http://www.stackoverflow.com/questions
        equal
                http://www.stackoverflow.com/

---

您好，您能告诉我我的示例的代码是什么样子的吗？当我使用您的示例作为模板执行

foreach

时，我会收到错误，例如“arg 1的类型必须是散列（而不是数组解引用）”？感谢您的帮助，如果我使用

foreach my$here（key%{$content\u length}{print（“key is'$here'\n”）；}

，我将无法获取一些数据？但是当我使用

来处理我的$key（key（@{$content_length}））{print（“key是'$key'\n”）；

}？@perl用户时就不是了，很抱歉这是一个打字错误。。。应该是

键（%{$content\u length}）

，如您所知。我在上面更新了我的答案。@perl user，这回答了你的问题吗？@perl user，你一定是打错了什么。我测试了这段代码，请参见上面的编辑。它起作用了。