[Catalyst] Catalyst::Model::CDBI::Sweet, Class::DBI::Loader and inheritance

[michael reece]

What I do to get around similar problems is unshift my own Base class  
into the ISA for the loaded classes, after the loader runs.

Something like:

sub new {
     my $class = shift;

     my $self = $class->NEXT::new(@_);

     foreach my $subclass ( $self->loader->classes ) {
         {
             no strict 'refs';
             unshift @{ $subclass . "::ISA" }, 'MyApp::CDBI::Base';
         }
         $subclass->autoupdate(0);
     }

     return $self;
}

and then MyApp::CDBI::Base can 'use base  
Catalyst::Model::CDBI::Sweet' ..

Maybe something similar will work for you..?

On May 4, 2005, at 8:42 AM, Will Hawes wrote:

> I want to use the improved search() method in  
> Catalyst::Model::CDBI::Sweet as the default for my model classes  
> (e.g. Hops::M::CDBI::Beer in the Hops application). This can be  
> made to work if package, use and require statements for each model  
> class are hardcoded (as in "Synopsis" in the POD for Sweet). Under  
> these circumstances the desired functionality can be achieved by  
> dropping in "use Catalyst::Model::CDBI::Sweet" in place of "use  
> Class::DBI". But I do not want to hard code this sort of stuff.
>
> Using Class::DBI::Loader introduces a problem. Class::DBI::Loader  
> makes all generated classes inherit from Class::DBI::mysql (or  
> Class::DBI::SQLite, etc, depending on your rdbms). You can still  
> inherit from Sweet explicitly:
>
> Class::DBI::Loader->new(
>     additional_base_classes => qw/Catalyst::Model::CDBI::Sweet/,
>     ...
> );
>
> But additional_base_classes adds to the end of @ISA. Since perl  
> reads @ISA from left to right, in this case the inheritance order is
>
> 1) Class::DBI::mysql
> 2) Catalyst::Model::CDBI::Sweet
>
> Calling $generated_class->search() will therefore still call  
> Class::DBI->search() rather than Catalyst::Model::CDBI::Sweet- 
> >search().
>
> The ideal solution would be to integrate the great stuff in  
> Catalyst::Model::CDBI::Sweet into Class::DBI, but Class::DBI's  
> author seems not to agree on at least one of the ideas (see the  
> recent thread on the CDBI mailing list "search() without search  
> criteria"), so the alternative is to change the inheritance order.
>
> I have tested this by hacking Class::DBI::Loader->_load_classes()  
> to generate something along the lines of:
>
> use base qw[Catalyst::Model::CDBI::Sweet Class::DBI::mysql ...];
>
> Now <generated_class>->search() calls  
> Catalyst::Model::CDBI::Sweet::search() rather than  
> Class::DBI::search(). I have not seen any adverse side effects yet.
>
> It might be useful if Class::DBI::Loader allowed classes to be  
> added to the start of @{ $generated_class }::ISA as well as the  
> end, to allow full control of the inheritance order. Maybe  
> something along the lines of
>
> Class::DBI::Loader->new(
>     base_classes => [Catalyst::Model::CDBI::Sweet], # <- added to  
> @ISA before Class::DBI::mysql and additional_base_classes
>     ...
> );
>
> Comments appreciated.
>
> Regards
>
> WH
>