I wrote my first module wrapping DBI years ago, and have used it on a few projects. Basically I've done this for two general objectives. The first is to wrap the DBI->connect call with a connect of my own, using a different name (such as db_connect). The purpose of custom connect isn't to muddle with DBI's internal connection mechanics, but just to handle things like providing some default values and/or retry connecting a few times. Inside my connect method I use DBI->connect and then store the $dbh as an attribute in the the object I bless into my own class and then return. The second reason is to provide a few special methods which all operate on a database. In no place am I trying to override existing DBI methods, just add new ones.

So far I have accomplished this fine by writing my custom DB class as a wrapper. In my custom methods I would use $self->{DBH}->prepare for example, and I use AUTOLOAD to simply pass any call not recognized in my module on to DBI:

sub AUTOLOAD {
    my $self = shift;
    my $call = $AUTOLOAD;
    $call =~ s/.*:://;
    
    return $self->{DBH}->$call(@_);
} # AUTOLOAD

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But I find myself in the middle of a moderate rewrite of an old project too long neglected. While the rest of the modules in the project are becoming more carefully designed classes, I feel an urge to do the same with my custom DBI wrapper, making it instead a subclass of DBI. This would allow me drop AUTOLOAD, but how would it effect my custom methods? If I read the docs correctly, $self->{DBH}->prepare() would just become $self->prepare(); OK, minor improvement.

Which leaves making the database connection, and this is where I found the docs (or mostly the ancillary articles on the subject) a bit confusing, giving some dire words of caution. ... Can I continue to use my own connect method, leaving DBI's available to the user if needed, and just replace $self{DBH} = DBI->connect(...) with $dbh = DBI->connect(..., { RootClass => 'MySubDBI' }) and return that connection handle instead of blessing it myself? Would it be more prudent to override DBI's connect method, calling SUPER::connect internally?

So fellow monks, besides hoping someone with experience could provide advice or sample snippets clarifying my questions above, I humbly ask you: Are the gains of sublassing DBI over wrapping it worth the effort given my simple needs?

Thanks!

In reply to Subclassing DBI instead of wrapping by spq

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