你如何正确处理数组中的哈希？

概述我有一系列哈希： my @questions = ( {"Why do you study here?" => "bla"}, {"What are your hobbies?" => "blabla"}); 我尝试循环它： foreach (@questions) { my $key = (keys $_)[0]; $content .= "\\section{$ 我有一系列哈希：

my @questions = (    {"Why do you study here?" => "bla"},{"What are your hobbIEs?" => "blabla"});

我尝试循环它：

foreach (@questions) {    my $key = (keys $_)[0];    $content .= "\section{$key}\n\n$_{$key}\n\n";}

给我

Use of uninitialized value in concatenation (.) or string at
convert.pl line 44.

错误来自哪里？

解决方法 Gilles already explained如何使用您当前的数据结构,但我建议您完全使用不同的数据结构：简单的哈希.

#!/usr/bin/perluse strict;use warnings;use 5.010;my %answers = (    "Why do you study here?" => "bla","What are your hobbIEs?" => "blabla");while (my ($question,$answer) = each %answers) {    say "Question: $question";    say "Answer: $answer";}

输出：

Question: Why do you study here?Answer: blaQuestion: What are your hobbIEs?Answer: blabla

我发现这比哈希数组更容易使用,每个哈希只包含一个键/值对.

如果您想以某个(非排序)顺序遍历哈希,则有几个选项.简单的解决方案是按照您要访问它们的顺序维护一组键：

# In the order you want to access themmy @questions = ("What are your hobbIEs?","Why do you study here?");my %answers;@answers{@questions} = ("blabla","bla");foreach my $question (@questions) {    say "Question: $question";    say "Answer: $answers{$question}";}

输出：

Question: What are your hobbIEs?Answer: blablaQuestion: Why do you study here?Answer: bla

另一种选择是使用Tie::IxHash(或更快的XS模块Tie::Hash::Indexed)按插入顺序访问密钥：

use TIE::IxHash;tIE my %answers,"TIE::IxHash";%answers = (    "Why do you study here?" => "bla",$answer) = each %answers) {    say "Question: $question";    say "Answer: $answer";}

输出：

Question: Why do you study here?Answer: blaQuestion: What are your hobbIEs?Answer: blabla

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