AFNetworking 2.0, saving download state with CoreData (MagicalRecord)

Question

i'm having an issue with a app that uses AFNetworking 2.0 and MagicalRecord. This app downloads data from a little JSON API in a podcast site and stores every podcast episode in a Podcast entity.

This Podcast Entity has another entity called PodcastDownload that keep information when a podcast is downloading (Download status and progress). In this PodcastDownload entity i use KVO to update this information observing the NSProgress object and state from the NSURLSessionDownloadTask. This works fine.

But I have a problem when I try to save the download status in my data context with this method in a singleton instance called PodcastManager:

- (void)saveContext{

  [[NSManagedObjectContext defaultContext] saveToPersistentStoreWithCompletion:^(BOOL success, NSError *error) {

  if (success) {
    NSLog(@"Save OK");
  } else if(error) {
    NSLog(@"Error %@", error.description);
  }

 }];
}

When I call this method I get this EXC_BAD_ACCESS error in the AFURLSessionManager from AFNetworking, but saving seems tu run ok according to my log:

Context BACKGROUND SAVING (ROOT) is about to save. Obtaining permanent IDs for new 1 inserted objects

I don't know what is causing this error. I Also tried using MagicalRecord method saveWithBlock but I got the same result.

This is my source code for my KVO Observer inside PodcastDownload:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
 {
  if (context == PodcastDownloadContext) {

  if ([object isKindOfClass:[NSURLSessionDownloadTask class]]) {

    NSURLSessionDownloadTask *task = (NSURLSessionDownloadTask *) object;



    if (task.state == NSURLSessionTaskStateRunning) {
      [self setStatus:PodcastDownloadRunning];
      [[PodcastManager sharedManager] saveContext];
    }

    if (task.state == NSURLSessionTaskStateSuspended) {
      [self setStatus:PodcastDownloadSuspended];
      [[PodcastManager sharedManager] saveContext];
    }

    if (task.state == NSURLSessionTaskStateCanceling) {
      [self setStatus:PodcastDownloadCanceling];
      self.downloadTask = nil;
      self.data = nil;
      self.progress = 0;
      [[PodcastManager sharedManager] saveContext];
    }

    if (task.state == NSURLSessionTaskStateCompleted) {

      if (self.status == PodcastDownloadCanceling) {
        [self setStatus:PodcastDownloadNotSet];
      } else {
        [self setStatus:PodcastDownloadCompleted];
        self.downloadTask = nil;
        self.data = nil;
        self.progress = 0;
        [[PodcastManager sharedManager] saveContext];
      }

      @try {
        [object removeObserver:self forKeyPath:NSStringFromSelector(@selector(state)) context:PodcastDownloadContext];
        [object removeObserver:self forKeyPath:NSStringFromSelector(@selector(fractionCompleted)) context:PodcastDownloadContext];
      }
      @catch (NSException * __unused exception) {}
    }

  }
 }
}

Thank you so much

Answer 1

Well, making some changes I find out a solution, but not the cause.

I had three entities in my Core Data stack (Podcast, PodcastDownload and PodcastPlayback). The main entity is Podcast and PodcastDownload was used to save information about the download, as I explained in my question.

What I did was take the attributes out from PodcastDownload and put them in the Podcast entity. And now seems to work as it should.

I don't know the exact cause of the error, but I think it was related with threading (sorry, I'm still a little noob with objective-c).

Thanks for all the help.