使用NSFetchedResultsController更新CoreData对象

Question

I made an app which uses Core Data and fetched results controller.

I can add CoreData objects and also delete them. Now I want to update an CoreData object via fetched results controller. I know that I have to fetch the objects and then I can change it. But because I'm still learning I don't know how to do this. Now I'd like to ask you how to do this?

Answer 1

When you fetch from CoreData, if you modify the results it will update the actual value within CoreData when you save it.

You'll want to first perform your fetch:

NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:@"Entity" inManagedObejctContext:moc]];
NSError *error = nil;
NSArray *results = [moc executeFetchRequest:request error:&error];

// error handling code

Once you have your results, you can modify the individual records...

MyEntity *entity = [results objectAtIndex:0];
entity.title = @"updated attribute";
// save context
[moc save:&error];

EDIT: In swift, it will be something along the lines of the following:

let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
var moc = appDelegate.managedObjectContext!

var fetchRequest = NSFetchRequest()
fetchRequest.entity = NSEntityDescription.entityForName("Entity", inManagedObjectContext: moc)

var error: NSError?
var results = moc.executeFetchRequest(fetchRequest, error: &error)

// error handling code

var entity: MyEntity = MyEntity()
entity.title = "updated attribute"

moc.save(&error)