Mysql Question posted in
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Need to iterate a hash returned from a mysql query

Ok – I have the following member function.


    sub GetCategories {
        my $sth = $dbh->prepare("SELECT CatID, CatName, CatLink FROM Categories");
        $sth->execute() or die $DBI::errstr;
        my $results = $sth->fetchall_arrayref({});

  

return($results);

`    $sth->finish();
}

I call it with:
my $Cats = $d2s->GetCategories();

my $vars = my $vars = {
    categories => $Cats,
};`

`

However my question is, how do I drill through that and extract the values in perl?

It is driving me nuts – below is the format of the $vars data from Data::Dumper –

$VAR1 = {
      'categories' => [
                          [
                            1,
                            'General',
                            './PostList.pl?cat=General'
                          ],
                          [
                            2,
                            'DevOps',
                            './PostList.pl?cat=DevOps'
                          ]
     };

I expected to see

 'categories' => [ { 'CatID' => 1, 'CatLink' => './PostList.pl?cat=General', 
'CatName' => 'General' }, { 'CatID' => 2, 'CatLink' => './PostList.pl?cat=DevOps', 'CatName' => 'DevOps' },

and so on

how do I for example print out the value for example DevOps in the second structure in a perl script. I can do it in a tt template just not perl

Tags:

2

Answers


  1. 0

    If a variable contains a reference, you need to dereference it to access the referenced thing.

    my $VAR1 = {
    categories => [
                      [
                        1,
                        'General',
                        './PostList.pl?cat=General'
                      ],
                      [
                        2,
                        'DevOps',
                        './PostList.pl?cat=DevOps'
                      ]
                  ]  # <- this was missing in your code!
};
print ${ $VAR1->{categories} }->[1][1];  # DevOps

    $VAR1 is a hash reference, we can dereference it using the arrow.

    $VAR1->{categories}

    The value associated with "categories" is a reference to an array reference, so we need to dereference it as a scalar to get an array reference

    ${ $VAR1->{categories} }

    then we can use the arrow again to get into the array.

    ${ $VAR1->{categories} }->[1]

    BTW, if the $sth->finish(); is placed after a return, it will never be executed.

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  2. 0

    You used fetchall_arrayref, and what you got is what that method does. There are other methods, such as fetchall_hashref and various select* methods that let you shape what the data structure will look like. It looks like you want one of them that returns the row as a hash.

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