Radar-27957917-ViewController.m

// Example code for https://openradar.appspot.com/radar?id=4975264899530752 since I can't attach 
// a zip there and am to lazy to create a git repo for the whole thing. 
// Create a standard iOS "Single View" application with Core Data in Xcode 7.3.1
// Create one Core Data entity called Thing with an integer "order" and a string "name"
// Hook up a simple view controller to these actions 

#import "AppDelegate.h"
#import "ViewController.h"
#import "Thing.h"

@interface ViewController () <NSFetchedResultsControllerDelegate>

@property (strong, nonatomic) NSFetchedResultsController *controller;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.controller = [self createFetchedResultsController];
    self.controller.delegate = self;
    [self.controller performFetch:NULL];
}

- (IBAction)createThings:(id)sender {
    NSManagedObjectContext *context = [self context];
    Thing *th1 = [NSEntityDescription insertNewObjectForEntityForName:@"Thing" inManagedObjectContext:context];
    th1.name = @"Hello";
    th1.order = @(1);
    Thing *th2 = [NSEntityDescription insertNewObjectForEntityForName:@"Thing" inManagedObjectContext:context];
    th2.name = @"World";
    th2.order = @(2);
    [[self appDelegate] saveContext];
}

- (IBAction)deleteThings:(id)sender {
    NSManagedObjectContext *context = [self context];
    NSArray <Thing *> *things = [self allThings];
    for (Thing *thing in things) {
        NSLog(@"Deleting thing %@", thing.name);
        [context deleteObject:thing];
    }
    [[self appDelegate] saveContext];
}

- (IBAction)toggleOrder:(id)sender {
    NSArray <Thing *> *things = [self allThings];
    for (Thing *thing in things) {
        if (thing.order.integerValue == 1) {
            thing.order = @(2);
        } else {
            thing.order = @(1);
        }
    }
    [[self appDelegate] saveContext];
}

- (NSArray <Thing *> *)allThings {
    NSManagedObjectContext *context = [self context];
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Thing"];
    NSError *error;
    NSArray <Thing *> *things = [context executeFetchRequest:request error:&error];
    if (!things) {
        NSLog(@"ERROR: %@", error);
    }
    return things;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (NSManagedObjectContext *)context {
    return [self appDelegate].managedObjectContext;
}

- (AppDelegate *)appDelegate {
    return (AppDelegate *)[UIApplication sharedApplication].delegate;
}

- (NSFetchedResultsController *)createFetchedResultsController {
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Thing"];
    request.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"order" ascending:YES]];
    
    NSFetchedResultsController * fetchController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:[self context] sectionNameKeyPath:nil cacheName:nil];
    
    return fetchController;
}

#pragma mark - NSFetchedResultsControllerDelegate

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    NSLog(@"%@", NSStringFromSelector(_cmd));
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {

    switch (type) {
        case NSFetchedResultsChangeInsert:
            NSLog(@"INSERT at %ld", newIndexPath.row);
            break;
            
        case NSFetchedResultsChangeDelete:
            NSLog(@"DELETE at %ld", indexPath.row);
            break;
            
        case NSFetchedResultsChangeUpdate:
            NSLog(@"UPDATE at %ld", indexPath.row);
            break;
            
        case NSFetchedResultsChangeMove:
            NSLog(@"MOVE from %ld to %ld", indexPath.row, newIndexPath.row);
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    NSLog(@"%@", NSStringFromSelector(_cmd));
    
}

@end