Perl：將元素推入到數組中用新變量值替換現有值

Question

我正在讀取csv文件，並且需要將行（第4行）中的值作爲數據庫中的關鍵元素。但該行包含逗號分隔的多個值。

1. 我使用Text :: CSV解析文件並將值分成第4行。

2. 然後將這些值插入一個數組並插入到一個新文件中，並保持其他值相同。

3. 但在循環的下一次運行中，值被替換爲新值。

   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; 
        } 
   

   自卸車結果是：

4. 因此我

的代碼（例如低於2）結束了的最後一個值的數組中的許多實例

#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是參考到數組。您反覆將此參考推入@newRows，因此@newRows最終將持有一組指向同一事物的指針。您需要在每次推入陣列時製作陣列的副本@newRows

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"; 

p.s.你過於複雜的東西：

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

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

Answer 2

my $row = \@oneRow; 

還有你的問題。 你持有一個參考@oneRow 所以，當你訪問的第4單元從$去參考行要更改@oneRow的值[3]

你也推該引用到列表中

，而不是打印自卸車，只是 打印@newRows

將闡明（你會看到相同的指針在那裏兩次）

Answer 3

我不知道你想在最後得到什麼。下面的代碼會給你multidimential陣列

#!/usr/local/bin/perl 


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 @newRows; 
my $userString = $oneRow[3]; 
my @userNewRow = split(/,/,$userString); 
foreach(@userNewRow) { 
    $oneRow[3] =~ s/.*/$_/; 
    push @newRows, [@oneRow]; 
} 

print Dumper \@newRows; 

輸出：

$VAR1 = [ 
      [ 
      'Vehicle Factory', 
      'D3', 
      '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export', 
      'ajj137035', 
      'ddb255570', 
      'mdb650204' 
      ], 
      [ 
      'Vehicle Factory', 
      'D3', 
      '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export', 
      ' mgp657301', 
      'ddb255570', 
      'mdb650204' 
      ] 
     ]; 

只得到那麼列表推式更改爲：

push @newRows, @oneRow; 

輸出：

$VAR1 = [ 
      'Vehicle Factory', 
      'D3', 
      '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export', 
      'ajj137035', 
      'ddb255570', 
      'mdb650204', 
      'Vehicle Factory', 
      'D3', 
      '2518, 1613, 1512, 1109, 912 bus, 712 bus, 613 Export', 
      ' mgp657301', 
      'ddb255570', 
      'mdb650204' 
     ]; 

我不明白創建一個的原因參考，所以我刪除了這部分。

這有助於您下次發佈您想要的輸出:)。