Inheriting from DBI

janDD has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I try to derive two classes from DBI with the following code:

use strict;
use warnings;
use DBI;

BEGIN{
  package MyDBI;
  our @ISA = ('DBI','MyDBI::st');

  sub connect {
    my $class=shift;
    my ($db,$user,$pw) = @_;
    my $self = DBI->connect($db,$user,$pw, { RaiseError => 1  } );
    bless $self;
    return $self;
  }
}

# ----------------------------------------
BEGIN {
  package MyDBI::st;
  our @ISA = ('DBI::st');
  
  sub query {
    my $class = shift;
    my $self = $class->prepare("SELECT * FROM `table` LIMIT 2");
    $self->execute();
    bless $self;
    return $self;
  }
}

my $dbh = MyDBI->connect("x","y","z"} );
my $sth = $dbh->query();
[download]

and perl gives the answer:

Can't locate auto/MyDBI/prepare.al in @INC (@INC contains ....) at lin
+e DB.pm line 29
[download]

I tried a couple of things, including using SUPER:: and different settings of @ISA but I don't find a solution. Thanks for your help, Jan

Comment on Inheriting from DBI Select or Download Code

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Re: Inheriting from DBI by runrig (Abbot) on Mar 02, 2011 at 15:58 UTC
Well, for one thing, you're reblessing a database handle (which is not of class DBI, it's something like DBI::db) into a class that inherits from DBI and DBI::st, so that it's not even a database handle anymore. See inheritance not working as expected	[reply]
Re: Inheriting from DBI by Corion (Patriarch) on Mar 02, 2011 at 15:51 UTC
What problem are you trying to solve by inheriting from DBI? I would (if at all) aggregate a DBI object (rep. a database handle, as returned from DBI::connect) into my object. DBI itself provides very little in the way of methods itself, mainly the `->connect` method. Most methods (like `->prepare` and `->fetch*` live in the database drivers (DBD::), and you can't easily inherit them (nor does that make sense to me). If you really want a simple way to keep your database handle, look at Class::DBI. A more complex way is DBIx::Class, but there are many other modules that live in the DBIx namespace that provide enhancements or different APIs to DBI.	[reply] [d/l] [select]
Re^2: Inheriting from DBI by janDD (Acolyte) on Mar 02, 2011 at 18:50 UTC
Well, the reason I am trying to do that is because I have to connect often to a database which is not very reliable in the sense that only one our of five connections is successful. So I want to enhance the connect, prepare, ... statements with some errorhandling (trying to reconnect several times, writing an error message by mails etc..) I am doing this now with simple functions, but I thought, a class is more appropriate ... J.	[reply]
Re^3: Inheriting from DBI by jeffa (Bishop) on Mar 02, 2011 at 19:07 UTC
Perhaps DBIx::Connector might offer a solution for you? jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l] [select]
Re^3: Inheriting from DBI by runrig (Abbot) on Mar 03, 2011 at 15:52 UTC
Your class doesn't need to inherit from DBI, it just needs to return a database handle. I've written lots of wrappers that connect to some default database in some default way that goes something like: `package MyDBI; use DBI; sub connect { ...get args my $dbh; ...do stuff $dbh = DBI->connect(...); ...do more stuff return $dbh; }` [download]	[reply] [d/l]