崩溃后核心数据为空

Question

I'm simulating a crash to test out how my app responds and noticed that my core data is empty when relaunching the app. Until now, using core data and NSFetchRequest has been working perfectly - I can terminate the app or turn off the phone and the data always remains. I'm using core data to store the URLS to audio files stored in NSFileManager . When I relaunch the app, I can see that the files are still in NSFileManager but NSFetchRequest returns a count of zero and my tableview is empty. Anyone experience this before?

EDIT: I've been simulating crashes using these two lines:

    NSArray *array = @[];
    array[1];

In viewDidLoad of my main view controller, I call the following:

self.managedDocument = [OSManagedDocument getInstance];
[self.managedDocument setUpDocument];  

managedDocument is a singleton that contains all my methods for data management.

@property (nonatomic, strong) NSManagedObjectContext * managedObjectContext;


+(OSManagedDocument*) getInstance
{
    static OSManagedDocument* _instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [[OSManagedDocument alloc] init];
    });
    return _instance;
}

-(void) setUpDocument
{

    if(self.document == nil)
    {
        NSFileManager * fileManager = [NSFileManager defaultManager];
        NSURL * documentsDirectory = [[fileManager URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] firstObject];
        NSString * documentName = @"MyRecordings";
        self.url = [documentsDirectory URLByAppendingPathComponent:documentName];
        self.document = [[UIManagedDocument alloc] initWithFileURL:self.url];


        BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:[self.url path]];

        if(fileExists)
        {
             [self.document openWithCompletionHandler:^(BOOL success) {
                if(success)
                {
                    [self documentIsReady];

                }

             }];
        }
        else
        {
             [self.document saveToURL:self.url forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success){
                if(success)
                {
                     [self documentIsReady];

                }
                else
                {
                    NSLog(@"Fail");
                }

            }];

        }
    }
}

-(void) documentIsReady
{

    if(self.document.documentState ==UIDocumentStateNormal)
    {
        self.managedObjectContext = self.document.managedObjectContext;
        NSLog(@"context is ready");
        [self fetchControllerFiles];
        [self recordingCount];
    }
}

-(int) recordingCount
{

    NSFetchRequest * request = [NSFetchRequest fetchRequestWithEntityName:@"Recording"];
    NSError *error;
    request.predicate = nil;
    request.sortDescriptors =nil;
    NSArray * recordings = [self.managedObjectContext executeFetchRequest:request error:&error];

    NSLog(@"recordings count %lu", (unsigned long)recordings.count);
    return (int)[recordings count];
}

When my app relaunches after a crash, I call the following:

 -(void) appBecameActive:(NSNotification *)notification
 {
     self.managedDocument = [OSManagedDocument getInstance];
 }

I call this method to add to core data

-(void) saveRecording:(NSMutableDictionary*) recordPackage inManagedObjectContext:(NSManagedObjectContext*) context
{

    Recording * recording = [NSEntityDescription insertNewObjectForEntityForName:@"Recording" inManagedObjectContext:context];

    recording.trackTitle = [recordPackage objectForKey:@"track label"];
    recording.audioURL = [[recordPackage objectForKey:@"audioURL"] absoluteString];
    recording.timeAdded = [NSDate date];
    recording.waveData = [recordPackage objectForKey:@"waveData"];
    recording.minAmpl = [recordPackage objectForKey:@"minAmpl"];
    recording.recordingNumber = [recordPackage objectForKey:@"recordingNumber"];


}

Answer 1

I've been counting on auto-save to take care of the saving and it worked fine until I started forcing crashes to see how the app recovered. Since the data was disappearing after every crash, I decided to try and save manually and it worked. Now the data appears even after a forced crash. I'm assuming this means auto-saving wasn't occurring in time. Not exactly sure how to explain it, but saving the context manually resolved my issue.

[self.document saveToURL:self.document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success) {
    if(success)
    {
        NSLog(@" NEW FILE SAVED");
    }
    else
    {
        NSLog(@"FAIL TO SAVE");
    }

}];