[CDBI] re-casting cdbi classes?

William Ross will at spanner.org
Thu Mar 23 09:52:19 GMT 2006


On 23 Mar 2006, at 01:33, Matt S Trout wrote:

> William Ross wrote:
>> On 18 Mar 2006, at 22:35, Ben Lavender wrote:
>>> Hi all,
>>>
>>> I've come across a situation where a client needs a change in
>>> requirements which would, ideally, require a slight slight breaking
>>> out of one class into a base class and two sub classes.  Put  
>>> shortly,
>>> I have an event which is based on due dates right now, but some
>>> classes of events are turning up which need to be done based on
>>> mileage instead.
>> Class::DBI doesn't like data classes to inherit from one another,  
>> and I very much doubt that it would like objects to switch from  
>> one data class to another after they've been retrieved. I'm sure  
>> it could be made to work, but the way cdbi holds closures at class  
>> level and its increasing use of plugins make it fairly horrible to  
>> debug that kind of code, or it does for me anyway.
>
> Inheritance was fine as of 0.96 before Tony started doing Odd  
> Things With Closures. Class::DBI::Frozen::301 may work here.

As far as I remember Odd Things With Closures have been a key part  
(and/or goal) of the Class::DBI project ever since the early Schwern  
versions, but it's true that they don't achieve their full  
incomprehensibility until combined with Tony's enthusiasm for  
pluggable overrides.

> DBIx::Class' inflate_result method which can be overridden to  
> rebless trivially is a better solution, but probably impossible to  
> backport.
>
>> My advice, based on 8ish years of repeatedly trying to bend cdbi  
>> out of shape, is don't. Do it the official cdbi way or find  
>> another ORM that matches your problem better: there's plenty of  
>> choice now.
>
> I've bent CDBI out of shape successfully a fair few times

Me too, and it can be good healthy fun. In this case the approach  
that Perrin suggested sounds excellent and very workable. I just  
wanted to sound a note of caution because in my experience once  
you've hacked a chunk out of cdbi you have to pay very close  
attention to every point release, and who has that kind of time any  
more? Whereas if you stay within the boundaries of normal use, it's  
actually pretty good at continuing to work.

will





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