Re: Callbacks registered on class, not instance?

Date sent:      	Mon, 9 Jul 2012 12:36:27 +0200
From:           	Michael Ludwig <[email protected]>
To:             	[email protected]
Subject:        	Callbacks registered on class, not instance?

> There's a huge perl process running, and we don't have access to the
> source code. We only have access to a loader script, which starts the
> entire process.
> 
> This process is doing lots of SQL via DBI. We'd like to change that SQL
> a little bit. This can be done via DBI callbacks as described in the
> manual:
> 
> http://search.cpan.org/~timb/DBI-1.622/DBI.pm#Callbacks
> 
> Callbacks are registered on DBI object instances. When the process is
> started we don't have access to handles, they have not been created yet.
> 
> However, in theory, we could load the DBI module in the loader script
> so the DBI code would be there, and then we could register callbacks on
> the *class*, not on the *instance*, and they would be called *from* the
> instance. In other words, global callbacks.
> 
> In practice it looks like this isn't supported. Or is it?
> 
> Michael

Hack it. Something like

use DBI;

{
  my $old_connect = \&DBI::connect;
  *DBI::connect = sub {
    my $connection = $old_connect->(@_) or return;
    do anything you like with the connection
    return $connection;
  }
}


Jenda
===== [email protected] === http://Jenda.Krynicky.cz =====
When it comes to wine, women and song, wizards are allowed 
to get drunk and croon as much as they like.
	-- Terry Pratchett in Sourcery