Question

this is my first foray into subclassing with perl and I am wondering why I am getting this simple error…

“Can’t locate object method “prepare” via package “WebDB::st” at /home/dblibs/WebDB.pm line 19.”. It seems to find the module WebDB ok, but not the prepare subroutine in ::st
First here’s my package (both packages are in one file, WebDB.pm)

package WebDB;
use strict;
use DBI;

sub connect {
    my $dbh = (DBI->connect ("DBI:mysql:test:127.0.0.1", "root","",
                    { PrintError => 1, RaiseError => 0 }));
    return bless $dbh, 'WebDB::st';
}

package WebDB::st;
our @ISA = qw(::st);
sub prepare {
    my ($self, $str, @args) = @_;
    $self->SUPER::prepare("/* userid:$ENV{USER} */ $str", @args);
}


1;

I also tried replacing the “our @ISA = qw(;;st)” with “use base ‘WebDB'” and same problem.
I’m thinking it’s probably something very simple that I’m overlooking. Many thanks! Jane

Answer 1

Subclassing DBI has to be done just right to work correctly. Read Subclassing the DBI carefully and properly set RootClass (or explicitly call connect on your root class with @ISA set to DBI). Make sure you have WebDB::st subclassing DBI::st and a WebDB::db class subclassing DBI::db (even if there are no methods being overridden). No need to rebless.

Avoid using base; it has some unfortunate behavior that has led to its deprecation, particularly when used with classes that are not in a file of their own.
Either explicitly set @ISA or use the newer parent pragma:

package WebDB;
use parent 'DBI';
...
package WebDB::db;
use parent -norequire => 'DBI::db';
...
package WebDB::st;
use parent -norequire => 'DBI::st';
...