nsfetchedresultscontroller

问题 First time that I'm using UICollectionView, and I'm having some difficulties. Especially with updating and deleting cells (will focus on delete here, hopefully the came cause), with data from a NSFetchResultController . I have made a custom cell in in interface builder as part of a storyboard like this: I have a custom UICollectionViewCell subclass with the following properties: @property (strong, nonatomic) IBOutlet UIButton *deleteButton; @property (strong, nonatomic) IBOutlet UITextField

问题 I feel as if this should be very simple, but it's behaving strangely. I have 3 entities, with a relationship as such Entity A <-->> Entity B <<--> Entity C I have an NSFetchedResults controller and I'm trying to filter the results of Entity A using the following predicate. [NSPredicate predicateWithFormat:@"NONE entityB.entityC == %@", self.entityC]; When I try and run the app, the output shows no results. I can alter the predicate slightly to: [NSPredicate predicateWithFormat:@"ANY entityB

问题 CoreData and ResultsController make the job really easy. But... Here is the situation: I have a functional resultsController in one tableView. When selecting a row, I go to another tableView that will show the child entity. With coreData, the child entity is ready to use. But how do I start another resultsController with this child entity? Do I need to fetchRequest again for this new resultsController using predicate to filter? Parent TablewView: Select row on resultsController -> Child

问题 Trying to track down this error I get when I have NSZombieEnabled . I get an EXC_BAD_ACCESS when the fetched results controllers attempts to execute a fetch. Debugger says: -[CFNumber retain]: message sent to deallocated instance 0x6e88d10 Backtrace says: #0 0x014bbe1e in ___forwarding___ () #1 0x014bbce2 in __forwarding_prep_0___ () #2 0x0145c490 in CFRetain () #3 0x0147929a in CFNumberCreate () #4 0x00b221ed in -[NSPlaceholderNumber initWithShort:] () #5 0x00b2216a in +[NSNumber

问题 I fetch data from a Core Data-base and present them in a UITableView . I use a NSFetchedResultController to fetch the data. I want the user to be able to search in the database, and to do that I use a NSPredicate . The data is presented in the UITableView and everything works well until I set the NSPredicate to the NSFetchedResultController . I use this in the ViewDidLoad method: self.fetchedResultsController = nil; fetchedResultsController_ = nil; NSError *error = nil; if (![[self

问题 I have a NSFetchedResultsController which displays data in a UITableView. I'm using the boiler plate code provided by Xcode when choosing to create a Core Data project. I added the following predicate to the NSFetchRequest the NSFetchedResultsController uses (before NSFetchedResultsController is initialized): NSPredicate *predicate = [NSPredicate predicateWithFormat:@"deleted == NO"]; [fetchRequest setPredicate:predicate]; Now in another location of my app, I set the deleted property like so

问题 I found this post question link, and I have done my best to convert it from Obj-C to Swift. When I added a new Entity and try to save it to CoreData, the app crashes and highlights this line: modifiedIndexPath = NSIndexPath(row: (indexPath?.row)!, section: 0) The error in green behind it is as follows: Thread 1; EXC_BREAKPOINT (code=1, subcode=0x100008b118) . I have no idea what this means, and the output panel only shows (llbd) in green as well. EDIT - I figured out that the app is crashing

问题 I have the following NSFetchedResultsController extension: extension NSFetchedResultsController { func tryObjectAtIndex(_ indexPath: IndexPath) throws -> AnyObject // ERROR HERE { do { try ObjC.catchException { return self.object(at: indexPath) // CAUSE } } catch { print("An error ocurred: \(error)") } } } in which ObjC is an Objective-C class (from here). Here's the .h : #import <Foundation/Foundation.h> @interface ObjC : NSObject + (BOOL)catchException:(void(^)())tryBlock error:(_

问题 I have a data model called Location . I use these as my section headers in a UICollectionViewController . Each location can display items inside these sections. I want to customise my section headers in viewForSupplementaryElementOfKind . But I can't figure out how to recive the correct Location objects from this method. I have tried things like: -(UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:

问题 I have two managed object contexts, A and B. These two contexts are kept in sync by merging changes from one to the other whenever they're saved (by monitoring NSManagedObjectContextDidSaveNotification ). I've verified that changes to A and B are merging properly. I have an NSFetchedResultsController monitoring updates to B. I find that certain updates to A do not result in the nsfrc firing on B. When a new managed object is created and added to A with the attributes the nsfrc is looking for