问题
I need to basically update my core data in a background thread without blocking UI and save it. After saving should reload table View to view the changes. So for doing this I thought of using
dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Add code here to do background processing
NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
self.backgroundManagedObjectContext = context;
if(self.managedObjectContext == nil)
self.managedObjectContext = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
self.backgroundManagedObjectContext.parentContext = self.managedObjectContext;
//update data
[self getDataFromFile];
dispatch_async( dispatch_get_main_queue(), ^{
// Add code here to update the UI/send notifications based on the
// results of the background processing
[[NSNotificationCenter defaultCenter] postNotificationName:@"ReloadAppDelegateTable" object:nil];
[context release];
});
});
and in getDataFromFile when I try to fetch data
if(![NSThread isMainThread])
{
NSEntityDescription *entity = [NSEntityDescription entityForName:@"LogDetails" inManagedObjectContext:self.backgroundManagedObjectContext];
[request setEntity:entity];
logs = [self.backgroundManagedObjectContext executeFetchRequest:request error:nil];
}
I get error * Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'LogDetails''
can anyone explain why I am getting this error
Also I have an another doubt whether to include it as background managedObjectContext or child managedObjectContext with parent as main thread managedObjectContext
回答1:
One NSManagedContext should only be used in one thread. passing NSManagedObject between threads are potentially unsafe.
来源:https://stackoverflow.com/questions/15269768/core-data-update-in-background