perl-workflow-devel

[Perl-workflow-devel] Persister::DBI subclassing issues

[Jim B. <cb...@bu...>]

I've just finished subclassing Workflow::DBI::Persister and ran into a 
few problems I wanted to share. Don't have any specific solutions just 
yet, just my work-arounds:

1) I don't think you can actually just subclass as shown here:

http://search.cpan.org/~jonasbn/Workflow-0.26/lib/Workflow/Persister/DBI.pm

unless you call SUPER::init because you'll get a $log not defined error 
when the code hits assign_generators. This is because the $log ||= 
get_logger is below the first $log call. I think if it gets moved up, 
the problem will be fixed:

sub assign_generators {
     my ( $self, $params, $driver ) = @_;
     $log ||= get_logger();
     $log->is_debug &&
         $log->debug( "assign_generators with $self, $params, $driver" );
     $self->SUPER::assign_generators( $params );
     return if ( $self->workflow_id_generator and
                 $self->history_id_generator );

move this up -->    $log ||= get_logger();
     my ( $wf_gen, $history_gen );

2) I think the 'assign_generators' example on the page has the params 
backwards. It shows:

     $self->assign_generators( $ds_config->{driver_name}, $params );

But I think that method wants $params first.

3) There doesn't seem to be an easy way to subclass the Persister and 
use ExtraData at the same time. I did it by subclassing ExtraData.pm, 
but I had to copy most of init and chop out a few things since I didn't 
want to call SUPER::init.

Maybe pull out the parts that load the extra values into a separate sub 
so if you subclass you just need to add a call to:

$self->load_extra_data();

to your init? Just a thought. I'm sure there are other solutions.

As I said, sorry I don't have actual patches right now. I just wanted to 
capture the info while it was fresh.


Jim


-- 
Jim Brandt
Administrative Computing Services
University at Buffalo

Re: [Perl-workflow-devel] Persister::DBI subclassing issues

[jonasbn <jo...@gm...>]

Hi Jim,

Thanks for sharing. It seems as if we have general problems with  
subclassing of some of the core classes.

I will put this on the task list, since I think it should be easier  
to subclass persisters among other things.


jonasbn

On 10/07/2007, at 19.30, Jim Brandt wrote:

>
> I've just finished subclassing Workflow::DBI::Persister and ran into a
> few problems I wanted to share. Don't have any specific solutions just
> yet, just my work-arounds:
>
> 1) I don't think you can actually just subclass as shown here:
>
> http://search.cpan.org/~jonasbn/Workflow-0.26/lib/Workflow/ 
> Persister/DBI.pm
>
> unless you call SUPER::init because you'll get a $log not defined  
> error
> when the code hits assign_generators. This is because the $log ||=
> get_logger is below the first $log call. I think if it gets moved up,
> the problem will be fixed:
>
> sub assign_generators {
>      my ( $self, $params, $driver ) = @_;
>      $log ||= get_logger();
>      $log->is_debug &&
>          $log->debug( "assign_generators with $self, $params,  
> $driver" );
>      $self->SUPER::assign_generators( $params );
>      return if ( $self->workflow_id_generator and
>                  $self->history_id_generator );
>
> move this up -->    $log ||= get_logger();
>      my ( $wf_gen, $history_gen );
>
> 2) I think the 'assign_generators' example on the page has the params
> backwards. It shows:
>
>      $self->assign_generators( $ds_config->{driver_name}, $params );
>
> But I think that method wants $params first.
>
> 3) There doesn't seem to be an easy way to subclass the Persister and
> use ExtraData at the same time. I did it by subclassing ExtraData.pm,
> but I had to copy most of init and chop out a few things since I  
> didn't
> want to call SUPER::init.
>
> Maybe pull out the parts that load the extra values into a separate  
> sub
> so if you subclass you just need to add a call to:
>
> $self->load_extra_data();
>
> to your init? Just a thought. I'm sure there are other solutions.
>
> As I said, sorry I don't have actual patches right now. I just  
> wanted to
> capture the info while it was fresh.
>
>
> Jim
>
>
> -- 
> Jim Brandt
> Administrative Computing Services
> University at Buffalo
>
>
>
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