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Re: NSPredicate Help
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Re: NSPredicate Help




On Apr 14, 2009, at 12:14 PM, Greg Robertson wrote:

I am using Core Data and have a two entity setup that in a simple form
could be modelled something like this:

Entity: Persons
- attribute: name
- attribute: birth
- relationship: cars (one to many with cars)

Entiry: Cars
- attribute: name

I would like to search for all persons not born on the date varDate
that have cars. I can do the search for all records/objects where the
date in the attribute birth is not equal to varDate, I can do this
with something like:
[request setPredicate:[NSPredicate predicateWithFormat:@"birth != %@",
self.varDate]];

but I am having difficulty figuring out how to write the predicate for
the relationship data, I would like something like:
[request setPredicate:[NSPredicate predicateWithFormat:@"cars != %@", NULL]];


Could someone help me write this predicate and show me the best way to
combine it with the first predicate?

I would do something like:

NSPredicate *birthPredicate = [NSPredicate predicateWithFormat:@"birth != %@", self.varDate]];
NSPredicate *carPredicate = [NSPredicate predicateWithFormat:@"cars.@count != 0"


NSPredicate *cp = [NSCompoundPredicate andPredicatewithSubpredicates: [NSArray arrayWithObjects:birthPredicate, carPredicate]];

[request setPredicate:cp];

I haven't actually checked that's quite right, but that's close.
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References: 
 >NSPredicate Help (From: Greg Robertson <email@hidden>)



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