Coredata 错误“ data: < fault >”

我尝试用下面的代码从 CoreData 中提取数据

NSFetchRequest *request = [[NSFetchRequest alloc] init];
request.entity = [NSEntityDescription entityForName:@"Cave" inManagedObjectContext:self.context];
request.predicate = [NSPredicate predicateWithFormat:@"(latitude > 0) AND (longitude > 0)"];


NSError *error;
NSLog(@"%@",[self.context executeFetchRequest:request error:&error]);
NSLog(@"%@",[error localizedDescription]);

CoreData 应该有9个匹配的对象，它会找到这9个对象。所以谓词应该可以工作，但是我在控制台中得到了这个

2011-09-05 07:41:42.267 CaveConditions[6930:11903] (
"<NSManagedObject: 0x7368060> (entity: Cave; id: 0x7367880 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p31> ; data: <fault>)",
"<NSManagedObject: 0x73547e0> (entity: Cave; id: 0x7356e20 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p40> ; data: <fault>)",
"<NSManagedObject: 0x73681e0> (entity: Cave; id: 0x7363e60 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p42> ; data: <fault>)",
"<NSManagedObject: 0x7368280> (entity: Cave; id: 0x7356be0 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p72> ; data: <fault>)",
"<NSManagedObject: 0x7368320> (entity: Cave; id: 0x733ad80 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p73> ; data: <fault>)",
"<NSManagedObject: 0x73683c0> (entity: Cave; id: 0x7333e70 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p91> ; data: <fault>)",
"<NSManagedObject: 0x7368480> (entity: Cave; id: 0x7361810 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p101> ; data: <fault>)",
"<NSManagedObject: 0x7368570> (entity: Cave; id: 0x7360110 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p105> ; data: <fault>)",
"<NSManagedObject: 0x7368610> (entity: Cave; id: 0x73303c0 <x-coredata://C825FC9D-3490-4D8A-A811-979B819A2EB6/Cave/p112> ; data: <fault>)"
)

它过去工作得很好，直到我在 Cave.m 中做了以下更改，即 Entity

我在 Cave.h 中作为代表添加了 MKAnnotation，并在 Cave.m 中添加了这段代码

- (CLLocationCoordinate2D)coordinate
{
CLLocationCoordinate2D location;
location.latitude = [self.latitude doubleValue];
location.longitude = [self.longitude doubleValue];
return location;
}

有办法调试吗？

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小开
最佳答案

This is expected behaviour, core data won't return full objects until you need to access the persistent values of the objects. Each of your returned objects will be a 'fault' until this point.

You can force the fetch request to return full objects using [request setReturnsObjectsAsFaults:NO], but in most cases what you have will be fine. Look at the documentation for NSFetchRequest for more information.

If you access one of the properties, core data will go to the persistent store and fetch the rest of your values, then you'll get the full description in the logs.

This seems to be such a common misunderstanding that I decided to write about it, here.

小开

I faced the same problem while pulling data from CoreData ! So, I followed the way @jrturton instructed and implemented it in Swift 3:

Step 1 : Add import CoreData

Step 2 : Add the code below . .

let context = ( UIApplication.shared.delegate as! AppDelegate ).persistentContainer.viewContext
var request = NSFetchRequest<NSFetchRequestResult>()
request = Your_Entity_Name.fetchRequest()
request.returnsObjectsAsFaults = false
do {
let arrayOfData = try context.fetch(request)
} catch {
// Handle the error!
}

Hope , it will help you . :)


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