Re: NSPredicateEditor

FROM : Chris
DATE : Fri Jun 27 03:48:05 2008

On Fri, Jun 27, 2008 at 10:09 AM, Peter Ammon <<email_removed>> wrote:

>
> On Jun 25, 2008, at 7:27 PM, Chris wrote:
>

>>
>> The net effect is that NSPredicateEditor can't display a predicate like
>>
>> NOT (foo = "bar")
>>
>>
>> A bug in NSPredicateEditor system perhaps? But surely someone would have
>> seen it before.
>>

>
> Hi Chris,
>
> NOT type compound predicates only support exactly one subpredicate, or at
> least they did when NSPredicateEditor was written.  For this reason, the
> default implementation of NOT expects the sole subpredicate to be an OR
> type.  So set this:
>
> NOT(OR(foo="bar"))



Ahh, this would explain why it hasn't been reported before.

However the BNF description of predicates does not impose that restriction:

http://developer.apple.com/documentation/Cocoa/Conceptual/Predicates/Predicates.pdf

And also, when you convert the predicate to a string, it doesn't show the
OR. The OR is apparently optimized away by the predicateFormat routine.
Since the only way to feasibly store a predicate is as a string, and then
parse it back in, its not really consistent.

I've worked around it by replacing the matchForPredicate routine of
NSPredicateEditorRowTemplate, which is where I think the actual problem
lies:


- (double)matchForPredicate:(NSPredicate *)predicate {

if ([predicate class] == [NSCompoundPredicate self]) {

return 0.5;

}

return 0.0;

}