core-data

问题 I am having the same issue described at this address http://www.cocoabuilder.com/archive/cocoa/288659-iphone-nsmanagedobjectcontext-save-doesn-crash-but-breaks-on-objc-exception-throw.html I am debugging an application that uses Core Data with multithreading, and I have a breakpoint on objc_exception_throw and it hits this breakpoint in the call to save. (line 2 in code) NSError *error = nil; [self.managedObjectContext save:&error]; if (error) { NSLog(@"Error : %@",error); } I don't have any

问题 I am having the same issue described at this address http://www.cocoabuilder.com/archive/cocoa/288659-iphone-nsmanagedobjectcontext-save-doesn-crash-but-breaks-on-objc-exception-throw.html I am debugging an application that uses Core Data with multithreading, and I have a breakpoint on objc_exception_throw and it hits this breakpoint in the call to save. (line 2 in code) NSError *error = nil; [self.managedObjectContext save:&error]; if (error) { NSLog(@"Error : %@",error); } I don't have any

问题 I'm building an app using Swift with Core Data. At one point in my app, I want to have a UITableView show all the objects of a type currently in the Persistent Store. Currently, I'm retrieving them and showing them in the table view using an NSFetchedResultsController . I want the table view to be sorted by a computed property of my NSManagedObject subclass, which looks like this: class MHClub: NSManagedObject{ @NSManaged var name: String @NSManaged var shots: NSSet var averageDistance: Int{

问题 Tracking a familial relationship in Core Data (1 parent entity + 2 types of children, one of which is recursive), trying to create a drop-menu in Interface Builder that lists the names of the parent entities so that the user can choose one to associate as the parent of the entry being edited. I've got the bindings all set, but when it runs it produces the following error text in the first slot of the menu: Relationship fault for ( <NSRelationshipDescription: 0x100143ed0> ), name parent,

问题 What I'm trying to accomplish is the following: I need to limit the amount of core data entries to 50. So if the user enters their 50th entry then the app would delete the oldest entry and add the new entry to the top of the stack. So basically, if the user never deletes entries and if there are 50 entries in core data then, when the user tries to add a new entry, the app would delete the oldest entry and add the user's new entry. Basically, I'm trying to have a history sort of thing but I

问题 I am new to core data. What I am trying to DO: I am trying to create a cocoatouch framework that has an app to add employee details and display them in a table view. So that i can add this framework to my main project to work independently. Issues I face: The frame work builds without any error. I have added the core data stack from swift 3 to the framework. But when i run the main project, the moment the framework loads the log displays "Failed to load model named Simple framework", "fetch

问题 I have a Core Data based iPhone application that needs to save 1000 managed objects on termination. This takes 8+ seconds, however, the OS kills the app if it does not complete in approx. 6 seconds. I don't want to save the objects earlier, because then the user has to wait 8 seconds longer for the results to display. Is it possible to somehow save the objects earlier in a background thread, while still having (read-only) access to the NSManagedObjectContext in the main thread to display the

问题 I'm struggling to find any information about creating backups of core data. My ultimate goal is to allow the user to create multiple backups, and restore from a selected backup. I've found a sample project that allows you backup/restore locally or via iCloud in Objective-C, but nothing in swift. Can anyone help? Or point me in the right direction. I don't even know where to start with this one. 回答1: I've never needed to do this but if I did this is what I'd do. To make backups At any time,

问题 I have the following model: parent is a to-one relationship (optional, no minimum, maximum=1). children is the inverse to-many relationship (optional, no minimum, no maximum). I added a new model version, where only the Entity Room is renamed to Classroom , all other entities are unchanged: I also created a mapping model for the migration, but the migration fails with the error message reason = "Can't find mapping model for migration"; The strange thing is that if the parent relationship is

问题 this is my core data model: I'm trying to get all LanguageEntries from a database for a given category.categoryName and languageset.languageSetName e.g. NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"LanguageEntry" inManagedObjectContext:del.managedObjectContext]; [fetchRequest setEntity:entity]; NSString* predicateString = [NSString stringWithFormat:@"Category.categoryName = %@ AND LanguageSet.languageSetName =