Perl 嵌套结构 [英] Perl nested structures

问题描述

我有一个关于 Perl 中复杂结构的问题

I have a question regarding complicated structures in Perl

my $data1 = [
  +{ id => 1, name => 'A' },
  +{ id => 2, name => 'B' },
  +{ id => 3, name => 'C' },
];

my $data3 = +{
   1 => +{ id => 1, name => 'A' },
   2 => +{ id => 2, name => 'B' },
   3 => +{ id => 3, name => 'C' },
};

我应该如何打印B"?那是什么样的数据结构?以及关于 Perl 嵌套结构(散列引用、数组引用等)的任何易于理解的好参考?

How should I print "B"? What kind of data structure is that? And any nice reference on Perl nested structures (hash references, array references, etc.) that is eay to understand?

提前致谢

推荐答案

尝试这样做:

print $data1->[1]->{name}; # ARRAY ref
print $data3->{2}->{name}; # HASH ref

这是从 perl ARRAY 和 HASH 引用中取消引用.

This is de-reference from a perl ARRAY and HASH ref.

-> 取消引用.只需要第一层地板"，例如:

The -> de-reference explicitly. It's only needed for the first "floor", ex :

print $data1->[1]{name};
print $data3->{2}{name};

也能用.第二个和更多是可选的.

Works too. The 2nd and more are optionals.

就像 Chris Charley 所说的，查看 数据结构教程

Like Chris Charley said, take a look to the tutorial on data structures

为了帮助您了解标量 ref 的外观，请使用 Data::Dumper，例如:

To help you understanding what your scalar ref looks like, use Data::Dumper , ex :

print Dumper $data1;
print Dumper $data3;

应该输出:

$VAR1 = [
          {
            'name' => 'A',
            'id' => 1
          },
          {
            'name' => 'B',
            'id' => 2
          },
          {
            'name' => 'C',
            'id' => 3
          }
        ];
$VAR1 = {
          '1' => {
                   'name' => 'A',
                   'id' => 1
                 },
          '3' => {
                   'name' => 'C',
                   'id' => 3
                 },
          '2' => {
                   'name' => 'B',
                   'id' => 2
                 }
        };

<小时>

对于 +{ } 语法，rra 给出了很好的回应:

---

For the +{ } syntax, rra gives a good response :

在可以将大括号视为代码块而不是匿名哈希引用的地方消除歧义，但很少需要这样做.我猜代码包含它们是出于一种错误的愿望，即希望在可能不明确的地方保持清晰和一致.

disambiguates in places where the braces could be taken to be a code block instead of an anonymous hash reference, but one rarely needs that. I'm guessing the code contains them out of a misplaced desire to be clear and consistent with places where it could be ambiguous.

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