Question

我正在使用github上的项目查找，让我使用NSFetchedResultsController和UICollectionView，项目为this

但是当我以这种方式保存新对象时：

NSManagedObject *doc = [NSEntityDescription insertNewObjectForEntityForName:@"Document" inManagedObjectContext:self.managedObjectContext];
                    [doc setValue:[title contents] forKey:@"docName"];
[doc setValue:element valueforKey:@"Element"]

[self saveContext];

我收到此错误：

 CoreData: error: Serious application error.  Exception was caught during Core Data change  processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  Can't perform collection evaluate with non-collection object. with userInfo (null)

我试图删除该项目，并且保存工作，所以我认为该项目中的问题，任何帮助？

Answer 1

我建议你导出NSManagedObject子类并声明你的对象如下：

// At top of the file:
#import "Document.h"

// In your Method:
Document *doc = (Document *)[NSEntityDescription insertNewObjectForEntityForName:@"Document" inManagedObjectContext:self.managedObjectContext];
doc.docName = title.contents;

NSError *error = nil;
[self.managedObjectContext save:&error];

if (error != nil) {
    NSLog(@"Oh no! Something terrible happened! Error: %@", error);
}
else {
    NSLog(@"Saved! Yay!");
}

使用UICollectionView和NSFetchedResultsController

1 个答案: