更改核心数据提取数组 [英] Making changes to Core Data fetched array

问题描述

这里是我所拥有的：

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription 
                               entityForName:@"NoteObject" inManagedObjectContext:appDelegate.managedObjectContext];

[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(parentNoteId == %@) AND (noteId!=rootNoteId)", appDelegate.currentNoteId];
[fetchRequest setPredicate:predicate];
NSError *error;

[appDelegate.arrayOfNotes setArray:[appDelegate.managedObjectContext executeFetchRequest:fetchRequest error:&error]];

NoteObject *note=[appDelegate.arrayOfNotes objectAtIndex:0];
[note.arrayOfTags addObject:someObject];

NSManagedObjectContext *context = [appDelegate managedObjectContext];
if (![context save:&error]) {
    NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}

提取工作正常，并将对象添加到 arrayOfTags 可以在用户界面中反映出来。但是，当我退出应用程序并返回时， arrayOfTags 缺少我添加的一个（但是它具有另外两个，所以我知道数组可以正常工作） 。

The fetch works fine, and adding an object to the arrayOfTags works and reflects in the UI. However, when I exit the app and come back, the arrayOfTags is missing the one that I added (but it has the other two, so I know the array is working properly). It's not saving for some reason.

（ NoteObject 是 NSManagedObject <的子类。 / code>和 arrayOfTags 是实体的可转换属性。）

(The NoteObject is a subclass of NSManagedObject, and arrayOfTags is a transformable property of the entity.)

我在做什么在这里错了吗？

Am I doing something wrong here?

编辑：这是我添加新笔记的方式，即使保存了arrayOfTags，也可以很好地保存它，并且在退出应用程序并返回时一切都保存了

Here's how I add a new note, which saves just fine, even with the arrayOfTags, and everything is saved when I exit the app and come back in.

NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSEntityDescription *noteEntity = [[appDelegate.managedObjectModel entitiesByName] objectForKey:@"NoteObject"];
NoteObject *tempNote = [[NoteObject alloc] initWithEntity:noteEntity insertIntoManagedObjectContext:context];
[tempNote.arrayOfTags addObject:@"tag1"];
NSError *error;
        if (![context save:&error]) {
            NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
        }

仅当我进行更改时，它才能正确保存。.

It's only when I make changes that it's not saved properly..

推荐答案

原来，我要做的就是在对数组进行更改后重新设置数组：

Turns out all I had to do was re-set the array after making changes to it:

NoteObject *tempNote = [[NoteObject alloc] initWithEntity:noteEntity insertIntoManagedObjectContext:context];
[tempNote.arrayOfTags addObject:@"tag1"];

[tempNote setArrayOfTags:tempNote.arrayOfTags]; //this is the magic line

NSError *error;
if (![context save:&error]) {
       NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}

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