Re: No overload magic

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On 16 Feb 2005, at 07:55, Karjala wrote:

> It's been said before on this list 
> (http://www.spanner.org/lists/cdbi/2004/09/15/7c3cf0f4.html)
>
> ...but I'd like to offer my feedback also.
>
> When I do comparisons between CDBI objects ($obj1 == $obj2), it worked 
> fine under cdbi 0.95 (it compared their keys), but it only sometimes 
> works under cdbi 0.96 (the rest of the times, it causes the error 
> message described in the linked message above).
>
> I think this is a bug.

In the message you cite the author was trying to perform comparisons on 
cdbi objects and assuming that ($x > $y) is the same as ($x->id > 
$y->id). There's no reason why that assumption should be correct: not 
all classes have a single key, and it's just as likely that you would 
want to compare some other column or a computed value, so cdbi leaves 
you to specify your own overloading. You can do that by adding more 
'use overload' instructions at the top of your data classes or base 
class:

use overload
	'>' => sub { shift->id },
	'<' => sub { shift->id },
	'==' => sub { shift->stringify_self },
	fallback => 1;

looking at the code, you can also specify the column(s) that a class 
stringifies to, which is a very nice touch. perhaps just adding:

My::Thing->columns(Stringify => qw(id));

will help?

best

will