[CDBI] Re: newbie: how can I put a placeholder on a query of a has_many relationship?

Victor Churchill victorchurchill at gmail.com
Thu Jun 7 21:52:14 BST 2007

Thanks Ed for such a quick reply!

On 07/06/07, Edward J. Sabol <sabol at alderaan.gsfc.nasa.gov> wrote:
> I don't think you're missing anything. There's no built-in way of doing this.
> It sounds like you want a more flexible implementation of has_many limiting:
> http://search.cpan.org/~tmtm/Class-DBI/lib/Class/DBI.pm#Limiting
> You can't really do complex limiting queries with that, however, AFAIK.

I'd seen that in the POD and thought "oh I wish it didn't just limit
on equality"!

> You have a couple options that I can see:
> 1. You *might* be able to develop your own Class::DBI::Relationship subclass
>    to implement this. Refer to HasMany.pm in the Class::DBI distribution
>    and/or Class::DBI::Relationship::HasManyOrdered on CPAN for examples. I'm
>    not aware of any implementations that do exactly what you want, but I
>    agree that it would be nice to have this capability. If you go this route
>    and get it working, please share the Relationship code with us!
> 2. Put the add_constructor() in the QG::Reading class and then add a simple
>    "wrapper method" in QG::ALM which takes the number of days as an argument
>    and passes that argument and any relevant object attributes along to the
>    QG::Reading constructor that you created and then returns the results. I
>    think this is what almost everyone does. It's usually only a 3-4 lines of
>    pretty simple code to implement such a method.

(1) sounds a little scary, though I could take a look at it. (2) looks
like it may be the way to go; I hadn't thought of the possibility of
adding home grown methods in the class. Definitely worth a look.

I've also seen a couple of refs to C::DBI::Sweet which I have not come
across previously and may be worth investigating.

Thanks again - will report back when I have some results.
> Hope this helps,
> Ed

Certainly did. I now feel less stupid than I did previously.

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