在perl中通过HASH迭代

Question

我用过:print Dumper $decoded,$decodedHASH变量在哪里,我把它作为输出.

    $VAR1 = {
              'Case_345' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   },
              'Case_512' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   },
              'Case_534' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   },
              'Case_552' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   },
              'Case_578' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   },
              'Case_466' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   },
              'Case_754' => {
                                     'Notes' => 'test2',
                                     'Submit_Date' => '2015-11-21 00:53:22 UTC',
                                     'Last_Resolved_Date' => ''
                                   }
            };

这是我尝试使用输出一些值来测试迭代HASH的内容.

    foreach my $key ( keys %decoded )
    {
         print "key: $key, value: $decoded{$key}\n";
    }

它不会通过$decoded变量进行迭代.我是perl的新手,有人可以帮助我.如果它有助于我通过转换字符串得到这个JSON::XS::decode_json($json_str).谢谢.

Answer 1

第一件事是它$decoded是一个包含哈希引用的标量变量,与哈希变量无关.要访问引用的哈希,必须取消引用它%decoded$decoded%$decoded

您必须始终 use strict并且use warnings 'all'在每个 Perl程序的顶部,特别是在向其他人寻求帮助之前.在这种情况下,这是一个简单的衡量标准,可以捕捉到你在%decoded没有声明的情况下使用过的事实

另外,值的哈希值都比较哈希引用,并打印出来会产生一种不到这样有用

key: Case_466, value: HASH(0xbf4840)
key: Case_534, value: HASH(0xc6dc00)
key: Case_552, value: HASH(0x280fce0)
key: Case_512, value: HASH(0xbf4930)
key: Case_345, value: HASH(0xd4c2f0)
key: Case_754, value: HASH(0x280fdd0)
key: Case_578, value: HASH(0x280fd58)

大概你想要每个哈希中所有字段的值？要在给定键和对应写入的哈希的引用的情况下访问哈希元素的值$hashref->{key},因此此代码将为您转储整个哈希

for my $key ( keys %$decoded ) {
  my $data = $decoded->{$key};
  print "key: $key, values:\n";
  for my $field ( qw/ Submit_Date Last_Resolved_Date Notes / ) {
    printf "    %-18s => %s\n", $field, $data->{$field};
  }
}

产量

key: Case_578, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2
key: Case_754, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2
key: Case_534, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2
key: Case_345, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2
key: Case_512, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2
key: Case_552, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2
key: Case_466, values:
    Submit_Date        => 2015-11-21 00:53:22 UTC
    Last_Resolved_Date => 
    Notes              => test2