push hash ref into array ref perl

Question

i am fetching data from a database...what i would like to achieve is for every data row fetched(id,title) to create a hash ref

{
   id => data->[0],
   title => data[1]
}

and push this hash ref into array ref in order to create the following format

 {  category => [
                   {
                    id => 1,
                    title => "title1"
                   },
                   {
                   id => 2,
                   title => "title2"
                   }
                  ]
              }

what i have made:

   my $productCategories->{category} = [];
    my $product = {};
    my $sth = $dbh->prepare(qq[SELECT id,title FROM ].DB_SCHEMA().qq[.product_categories]) || die $dbh->errstr;
    $sth->execute() || die $dbh->errstr;
    while(my $data = $sth->fetch){
        $product =  {
                    id      =>  $data->[0],
                    title   =>  $data->[1]
                    };
        push $productCategories->{category}, $product;
    }

but it is not working...

See also using push() on an array inside a hash

Håkon Hægland
– Håkon Hægland

2015-12-10 11:43:15 +00:00
Commented Dec 10, 2015 at 11:43 — Håkon Hægland
– Håkon Hægland, Commented Dec 10, 2015 at 11:43

Community · Accepted Answer · 2020-06-20 09:12:55Z

4

Turn on use strict; use warnings; and it'll tell you why.

push on reference is experimental

Not an ARRAY reference

Try:

push @{$productCategories->{category}}, $product;

Also: Be careful with declaring things you're pushing outside the loop - you should be ok in this case, but bear in mind you're pushing a reference. If you re-use variables, you can end up with pushing the same reference.

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Dec 10, 2015 at 10:55

Sobrique

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3 Comments

Sobrique Over a year ago

Does in my sample. But perhaps you need to be clearer what you mean by 'not working'.

tsiro Over a year ago

using warn Data::Dumper::Dumper(@{$productCategories->{category}}); i am getting this response: 'id' => 2 }; $VAR3 = { 'title' => 'pizza', 'id' => 3 }; $VAR4 = { 'title' => "\x{396}\x{3c5}\x{3bc}\x{3b1}\x{3c1}\x{3b9}\x{3ba}\x{3ac}", 'id' => 4 };

Sobrique Over a year ago

You need to pass a ref to Data::Dumper. print Dumper $productCategories should do the trick.

Dave Cross · Accepted Answer · 2015-12-10 13:14:48Z

4

DBI has many methods for fetching data. One of them is called fetchall_arrayref() and it will give you back the data in exactly the structure that you need - no need to build it up yourself.

my $sth = $dbh->prepare(qq[SELECT id,title FROM ] .
                        DB_SCHEMA() .
                        qq[.product_categories])
  || die $dbh->errstr;

$sth->execute() || die $dbh->errstr;

# Pass a hash ref to get each row back as a hash.
$productCategories->{category} = $sth->fetchall_arrayref({});

answered Dec 10, 2015 at 13:14

Dave Cross

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