我在没有NSFetchedResultsController
的情况下设置了CoreData,并且保存了所有内容。切换到NSFetchedResultsController
后,我在尝试保存图像时遇到了一个奇怪的错误。
以下是我用来保存图片的代码:
- (void)saveImage {
NSManagedObjectContext *context = [self managedObjectContext];
TimeTravelFeed *timeTravelFeed = [NSEntityDescription insertNewObjectForEntityForName:@"TimeTravelFeed" inManagedObjectContext:context];
NSData *imageData = UIImageJPEGRepresentation(self.thumbImage, 0.8f);
[timeTravelFeed setValue:imageData forKey:@"imageData"];
NSError *error = nil;
if (![self.managedObjectContext save:&error]) {
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
//[tableView reloadData];
}
以下是错误消息:
-[_PFExternalReferenceData compare:]: unrecognized selector sent to instance 0x1669fb40
2013-12-08 10:09:49.442 Time Travel[830:60b] CoreData: error: Serious application error. Exception was caught during Core Data change processing. This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.
-[_PFExternalReferenceData compare:]: unrecognized selector sent to instance 0x1669fb40 with userInfo (null)
2013-12-08 10:09:49.443 Time Travel[830:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[_PFExternalReferenceData compare:]: unrecognized selector sent to instance 0x1669fb40'
以下是NSFetchedResultsController的代码:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
DetailViewController *detailsViewController = [[DetailViewController alloc] init];
[self.navigationController pushViewController:detailsViewController animated:YES];
}
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath]
atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:@"TimeTravelFeed" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:@"imageData" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *theFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:managedObjectContext sectionNameKeyPath:nil
cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
答案 0 :(得分:2)
问题似乎在这里:
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:@"imageData" ascending:NO];
您无法对“二进制数据”属性进行排序。获取的结果控制器 需要一个排序描述符,所以你应该使用不同的属性,例如字符串,数字或日期。例如
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:@"creationDate" ascending:NO];
其中“creationDate”是一个属性(类型为“Date”)并在创建对象时设置:
[timeTravelFeed setValue:imageData forKey:@"imageData"];
[timeTravelFeed setValue:[NSDate date] forKey:@"creationDate"];
答案 1 :(得分:1)
转到您的DBfile,选择名为“TimeTravelFeed”的实体,然后选择“imageData”键。设置属性。