At 03:05 PM 4/19/01 -0400, Paul D. Smith wrote:
>Is this too advanced a question for [EMAIL PROTECTED]?
Pretty much :-) I'd try [EMAIL PROTECTED]
More below.
>I'm trying to create a subclass of the DBI class. My goal is twofold:
>
> 1) Override the connect method so that I can hide many of the details
> of connecting from the rest of my package, and
>
> 2) Add a few extra "helper" methods.
>
>I want to access my extra helper methods, plus all the standard DBI
>methods.
>
>My subclass has no data of its own, so I just wanted to use the normal
>DBI handle as the object reference.
>
>I did something like this:
>
> package My::DB;
>
> use strict;
> use vars qw(@ISA);
>
> use DBI;
>
> @ISA = qw(DBI);
>
> sub connect {
> my $self = shift;
> my $class = ref($self) || $self;
>
> #... figure connect info $data_source, $username, $password
>
> return $class->SUPER::connect($data_source, $username, $password);
> }
>
>
> sub MyMethod {
> my $this = shift;
>
> # ... do some stuff
> }
>
>Now when I do this:
>
> $dbh = My::DB->connect();
>
>it works, but this:
>
> $dbh->MyMethod();
>
>fails with "Can't locate object method "Send" via package My::DB at ...".
>
>Is this telling me that DBI was implemented using only the 1-arg form of
>bless? Can I not inherit from DBI?
It's using a two-arg form, but it's buried amidst a maze of calls between
DBI and a driver. So I think you're best off finding out what the
'approved' way of subclassing DBI is. I can't even find anything about it
in the DBI book.
>So, then I thought I'd try re-blessing it into my class, like this:
>
> sub connect {
> my $self = shift;
> my $class = ref($self) || $self;
>
> #... figure connect info $data_source, $username, $password
>
> my $this = $class->SUPER::connect($data_source, $username, $password);
>
> return bless($this, $class);
> }
>
>Now I can get to $dbh->MyMethod(), but I can't get to any of the DBI
>methods; for example $dbh->prepare() fails with:
>
> Can't locate auto/My/DB/prepare.al in @INC ...
>
>I can't even get there using SUPER; this also fails:
>
> sub MyMethod {
> my $this = shift;
>
> # ... do some stuff
>
> return $this->SUPER::prepare(...);
> }
>
>Gives me:
>
> Can't locate auto/My/DB/SUPER/prepare.al in @INC ...
>
>which seems strange to me.
>
>Anyway, can anyone help me make a subclass of DBI that does what I want?
>Do I have to write some kind of AUTOLOAD to do a delegator (or use
>Class::Delegate or something), as described in Camel? I was hoping that
>the @ISA thing would allow any method that wasn't known in my class to
>be automatically looked for in my parent classes... why doesn't that
>work?
>
>Thanks!
>
>--
>-------------------------------------------------------------------------------
> Paul D. Smith <[EMAIL PROTECTED]> HASMAT--HA Software Methods &
> Tools
> "Please remain calm...I may be mad, but I am a professional." --Mad
> Scientist
>-------------------------------------------------------------------------------
> These are my opinions---Nortel Networks takes no responsibility for them.
--
Peter Scott
Pacific Systems Design Technologies
http://www.perldebugged.com
