Re: Need some help with fetch requests
Re: Need some help with fetch requests
- Subject: Re: Need some help with fetch requests
- From: "Carter R. Harrison" <email@hidden>
- Date: Fri, 1 Feb 2008 15:41:05 -0500
On Feb 1, 2008, at 3:36 PM, Chris Hanson wrote:
On Feb 1, 2008, at 12:03 PM, Carter R. Harrison wrote:
Today I'm working with NSFetchRequests for the first time and I
need some help learning how to filter down the initial set of
managed objects that I want to search against.
Entity: File
Relationship: Messages
I assume you actually mean "messages" given that properties of
objects in Objective-C start with lower-case letters. :)
You assumed correctly. Thanks for making a note of this though.
My initial thought was to add more criteria to my predicate to help
narrow down the search base, but I'm not sure how the predicate's
criteria could traverse relationships.
Magic. :)
Do all of your relationships have appropriate inverses? If not,
they should. Then you could just use a predicate like this:
NSPredicate *fieldSearchPredicate = [NSPredicate predicateWithFormat:
@"(message.file IN %@) AND (value = %@)", files,
requestedFieldValue];
Use that in a fetch request on the Field entity and it should just
work. "files" should be an NSArray or NSSet of instances of your
File entity, or NSManagedObjectID instances representing instances
of your File entity.
Excellent! I had already made inverse relationship so your answer
should work. I'm not sure why I couldn't figure that out, but I do
appreciate it!
-- Chris
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