On 1/12/06 2:42 PM, "Cees Hek" <[EMAIL PROTECTED]> wrote:
> On 1/12/06, Sean Davis <[EMAIL PROTECTED]> wrote:
>> Cannot load ApacheAdmin::Model::User without a primary key (username) with a
>> non-null value or another unique key with at least one non-null value. at
>> test.pl line 9
>>
>> If I remove the inheritance from Catalyst::Model, everything works fine.
>> It's not too big a deal in practice--I don't NEED the catalyst::model
>> inheritance--but I'm curious why this doesn't work.
>
> <SNIP>
>
>> our @ISA = qw(Catalyst::Model Rose::DB::Object);
>
> You are probably running into multiple inheritance problems. Did you
> try reversing the order of those modules in @ISA to see if you get the
> same problem?
>
> Catalyst::Model inherits from Catalyst::Component, which inherits from
> Class::Accessor::Fast and Class::Data::Inheritable. So if there is a
> duplicated method that exists in Rose::DB::Object that also exists in
> one of those modules, then your Rose::DB::Object instance will end up
> calling the wrong method. perl uses a depth first search to find
> method names when using multiple inheritance, so anything in the
> Catalyst::Model tree will take precidence over the methods in
> Rose::DB::Object.
>
> Catalyst uses 'NEXT' to forward calls in a lot of places, so some of
> the method name conflicts 'may' still work, but any method that
> doesn't use NEXT means the real Rose::DB::Object method will never be
> called.
Thanks, Cees. In the meantime, I have heard from Matt Trout.
I thought about the NEXT call (and even tried to modify the code to use
NEXT, unsuccessfully), but I hadn't thought of the obvious point that Matt
brought to my attention. When Catalyst starts, it calls "new" on all its
components. Since the module was technically a catalyst component by
including Catalyst::Model in the @ISA, it was calling "new" on the
Rose::DB::Object, which is what is generating the error. Multiple
inheritance is pretty cool, but I see how it can become a problem if one
doesn't know exactly what is going on.
Sean
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