arrays - Perl:将元素插入数组用新的变量值替换现有值

Question

我正在读取一个 csv 文件，需要将一行(第 4 行)中的值作为数据库中的关键元素。但该行包含多个逗号分隔的值。

我用 Text::CSV 解析文件并在第 4 行拆分值。

然后将这些值推送到一个数组中并插入到一个新文件中，其他值保持不变。

但是在下一次循环运行中，该值被新值替换。

因此，我最终得到了数组中最后一个值的多个实例(在下面的示例中为 2)

编码 :

use Data::Dumper;
use strict;
my @oneRow = ('Vehicle Factory',
          'D3',
          '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export',
          'ajj137035, mgp657301',
          'ddb255570',
          'mdb650204'
          );
my $row = \@oneRow;
my @newRows;
my $userString = $row->[3];
        my @userNewRow = split(/,/,$userString);
        foreach(@userNewRow) {
            $row->[3] =~ s/.*/$_/;
            print Dumper $row;
            push @newRows, $row;
            print Dumper @newRows;
        }

倾销者结果是:

#comment: this is Dumper $row result of first run in loop
$VAR1 = [
          'Vehicle Factory',
          'D3',
          '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export',
          'ajj137035',
          'ddb255570',
          'mdb650204'
        ];
 #comment: this is the Dumper @newRows result of first run in loop
$VAR1 = [
          'Vehicle Factory',
          'D3',
          '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export',
          'ajj137035',
          'ddb255570',
          'mdb650204'
        ];
#comment: this is the Dumper $row result of 2nd run in loop 
$VAR1 = [
          'Vehicle Factory',
          'D3',
          '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export',
          ' mgp657301',
          'ddb255570',
          'mdb650204'
        ];
#comment: this is Dumper @newRows result of second run in loop 
the new value is inserted but the first value becomes same as new value
$VAR1 = [
          'Vehicle Factory',
          'D3',
          '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export',
          ' mgp657301',
          'ddb255570',
          'mdb650204'
        ];
$VAR2 = $VAR1;

Answer 1

$row是 引用 到一个数组。您反复将此引用推送到 @newRows所以@newRows最终将持有一组指向同一事物的指针。每次推送到 @newRows 时，您都需要复制该数组。

例如

my @arr = (1, 2, 3);
my $ref_a = \@arr;
my $ref_b = \@arr;

$ref_a->[0] = "test";
print $ref_b->[0]; # prints "test";

附言你把事情复杂化了:

my @row = ('Vehicle Factory', 'D3', '2518, ...', ...);
my @newRows = ();

for my $k (split /,\s*/, $row[3])
{
    push @newRows, [@row[0..2], $k, @row[4..$#row]];
}