[問題] CoreData relationship predicate
現有一個Entity為CompletdFrame
它有一個to-many relationship為peopleRead
欲fetch出 peopleRead個數為0的CompletedFrame
NSFetchRequest *fr = [NSFetchRequest fetchRequestWithEntityName:@"CompletedFrame"];
//只fetch peopleRead個數為0的CompletedFrame
fr.predicate = [NSPredicate predicateWithFormat:@"peopleRead.@count == 0"];
NSArray *framesIHaveNotRead = [_appDelegate.managedObjectContext executeFetchRequest:fr error:&error];
但是把framesIHaveNotRead印出來
卻有peopleRead個數不為0的CompletedFrame
是因為predicate不能針對relationship嗎？
<CompletedFrame: 0x1427c750> (entity: CompletedFrame; id: 0x1427ab00 <x-coredata://4FF961E4-8C79-488A-BB14-7A640F28A095/CompletedFrame/p7> ; data: {
fid = e9f527cc7a;
order = 0;
peopleRead = (
"0xc8726d0 <x-coredata://4FF961E4-8C79-488A-BB14-7A640F28A095/Friend/p1
);
readIconHidden = 0;
receiver = "0x14271710 <x-coredata://4FF961E4-8C79-488A-BB14-7A640F28A095/Receiver/p6>";
sender = "0x1267d170 <x-coredata://4FF961E4-8C79-488A-BB14-7A640F28A095/Friend/p4>";
sendingStatus = 2;
stickerTexts = (
"0x1827a870 <x-coredata://4FF961E4-8C79-488A-BB14-7A640F28A095/CompletedStickerText/p7>"
);
timestamp = "2013-11-21 02:35:08 +0000";
type = 1;
works = "<relationship fault: 0xc879e10 'works'>";
})
)
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