Question

我还没有掌握数组和散列，散列数组，散列哈希等之间的区别，所以我不知道下面的代码定义了什么。有人会告诉我哪些是好的吗？

my $col_props = [
    {   min_w   => 50,                                                 # Minimum column width.
        max_w   => 50,                                                 # Maximum column width.
        justify => 'left',                                             # One of left|center|right ,
        font    => $pdf->corefont( "Arial", -encoding => "latin1" ),
    },
    {   min_w   => 110,                                                # Minimum column width.
        max_w   => 110,                                                # Maximum column width.
        justify => 'left',                                             # One of left|center|right ,
        font    => $pdf->corefont( "Arial", -encoding => "latin1" ),
    },
    {   min_w   => 110,                                                # Minimum column width.
        max_w   => 110,                                                # Maximum column width.
        justify => 'left',                                             # One of left|center|right ,
        font    => $pdf->corefont( "Arial", -encoding => "latin1" ),
    },
];

但是，我真正的问题是，根据上面的代码，我如何动态填充$col_props？

Answer 1

$col_props是哈希数组的引用。

例如，第二个条目的最大列宽为

$col_props->[1]{max_w}

如何填充它取决于您想要做什么。假设您在%column_data中有一个列定义，那么您可以使用

将其推送（添加到数组末尾）

push @$col_props, \%column_data

修改或添加其中一个哈希的字段只需分配给它，例如

$col_props->[2]{min_w} = 20

Answer 2

$col_props是一个哈希数组。

分配中的$和[ ]表明$col_props是数组引用。

一种方法可能是这样的：

#!/usr/bin/perl -w


my $col_props = [
    {   min_w   => 50,                          # Minimum column width.
        max_w   => 50,                          # Maximum column width.
        justify => 'left'                     # One of left|center|right ,
    },
    {   min_w   => 110,                           # Minimum column width.
        max_w   => 110,                          # Maximum column width.
        justify => 'left'                       # One of left|center|right ,
    },
    {   min_w   => 110,                             # Minimum column width.
        max_w   => 110,                            # Maximum column width.
        justify => 'left'                           # One of left|center|right ,
    },
];

foreach my $ref (@{$col_props}) { #1 print
  print "min_w: ". $ref->{min_w} . "\n"
  . "max_w: " . $ref->{max_w} . "\n";
}

my %new_hash = ( # create a new hash to push
  min_w => 1,
  max_w => 2,
  justify => 'right'
);


push @{$col_props}, \%new_hash; # pushing the new_hash reference
print "\n";

foreach my $ref (@{$col_props}) { #2 print
  print "min_w: ". $ref->{min_w} . "\n"
  . "max_w: " . $ref->{max_w} . "\n";
}

#1 print:

min_w: 50
max_w: 50
min_w: 110
max_w: 110
min_w: 110
max_w: 110

#2 print:

min_w: 50
max_w: 50
min_w: 110
max_w: 110
min_w: 110
max_w: 110
min_w: 1
max_w: 2

为了更好地理解，请查看here。

动态填充嵌套的Perl哈希值和数组

2 个答案: