Setup a Core Data request and, instead of actually issuing the query, do the following: NSError *error = nil; NSUInteger count = [managedObjectContext countForFetchRequest:request error:&error]; if (!error) { return count; } else { return 0; } In practice, the method countForFetchRequest:error: returns the number of objects a given fetch request would have returned if it … Read more
Updating is simple as creating a new one. To update a specific object you need to set up a NSFetchRequest. This class is equivalent to a SELECT statetement in SQL language. Here a simple example: NSFetchRequest *request = [[NSFetchRequest alloc] init]; [request setEntity:[NSEntityDescription entityForName:@”Favorits” inManagedObjectContext:moc]]; NSError *error = nil; NSArray *results = [moc executeFetchRequest:request error:&error]; … Read more
You can declare your enum as @objc. Then it all automagically works. Here’s a snippet from a project I’m working on. // Defined with @objc to allow it to be used with @NSManaged. @objc enum AgeType: Int32 { case Age = 0 case LifeExpectancy = 1 } /// The age type, either Age or LifeExpectancy. … Read more
The result of a fetch is an array of managed objects, in your case [Event], so you can enumerate the array and delete all matching objects. Example (using try? instead of try! to avoid a crash in the case of a fetch error): if let result = try? context.fetch(fetchRequest) { for object in result { … Read more
“Optional” means something different to Core Data than it does to Swift. If a Core Data attribute is not optional, it must have a non-nil value when you save changes. At other times Core Data doesn’t care if the attribute is nil. If a Swift property is not optional, it must have a non-nil value … Read more
I also struggled with this and found a very nice and clean solution: You have to wrap the row in a separate view and use @ObservedObject in that row view on the entity. Here’s my code: WineList: struct WineList: View { @FetchRequest(entity: Wine.entity(), sortDescriptors: [ NSSortDescriptor(keyPath: \Wine.name, ascending: true) ] ) var wines: FetchedResults<Wine> var … Read more
To recap/Full guide: Before making any change, create a new model version. In Xcode 4: Select your .xcdatamodel -> Editor -> Add Model Version. In Xcode 3: Design -> Data Model -> Add Model Version. You will see that a new .xcdatamodel is created in your .xcdatamodeld folder (which is also created if you have … Read more
Though i agree with what you said, there is an ID mechanism behind core data. ID are indeed managed by Core-Data but you can retrieve them with : NSManagedObjectID *moID = [managedObject objectID]; For more informations see : Core Data Programming Guide
Here’s a class I created to perform a “deep copy” of managed objects: attributes and relationships. Note that this does not check against loops in the object graph. (Thanks Jaanus for the starting off point…) @interface ManagedObjectCloner : NSObject { } +(NSManagedObject *)clone:(NSManagedObject *)source inContext:(NSManagedObjectContext *)context; @end @implementation ManagedObjectCloner +(NSManagedObject *) clone:(NSManagedObject *)source inContext:(NSManagedObjectContext *)context{ … Read more
I finally got mine to work. Here is what I did. (Flights is one of my entities) I setup the xcdatamodeld as follows And then the entity as Then I used Editor -> Create NSManagedObject Subclass This creates two files for my flights entity Flights+CoreDataProperties.swift Flights+CoreDataClass.swift I renamed Flights+CoreDataClass.swift to Flights.swift Flights.swift is just import … Read more