NSData in CoreData is not saving properly - ios

Question

I am currently trying to store images I download from the web into an NSManagedObject class so that I don't have to redownload it every single time the application is opened. I currently have these two classes.
Plant.h
#property (nonatomic, retain) NSString * name;
#property (nonatomic, retain) PlantPicture *picture;
PlantPicture.h
#property (nonatomic, retain) NSString * bucketName;
#property (nonatomic, retain) NSString * creationDate;
#property (nonatomic, retain) NSData * pictureData;
#property (nonatomic, retain) NSString * slug;
#property (nonatomic, retain) NSString * urlWithBucket;
Now I do the following:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
PlantCollectionCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
Plant *plant = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.plantLabel.text = plant.name;
if(plant.picture.pictureData == nil)
{
NSLog(#"Downloading");
NSMutableString *pictureUrl = [[NSMutableString alloc]initWithString:amazonS3BaseURL];
[pictureUrl appendString:plant.picture.urlWithBucket];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:pictureUrl]];
AFImageRequestOperation *imageOperation = [AFImageRequestOperation imageRequestOperationWithRequest:request success:^(UIImage *image) {
cell.plantImageView.image = image;
plant.picture.pictureData = [[NSData alloc]initWithData:UIImageJPEGRepresentation(image, 1.0)];
NSError *error = nil;
if (![_managedObjectContext save:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
}
}];
[imageOperation start];
}
else
{
NSLog(#"Already");
cell.plantImageView.image = [UIImage imageWithData:plant.picture.pictureData];
}
NSLog(#"%#", plant.name);
return cell;
}
The plant information is present, as well as the picture object. However, the NSData itself is NEVER saved throughout the application opening and closing. I always have to REDOWNLOAD the image! Any ideas!? [Very new to CoreData... sorry if it is easy!]
thanks!
Edit & Update:
The image download is NOT nil and appears just fine after it was downloaded. It looks like the data returned by UIImageJPEGRepresentation is not nil also. My managedObjectContext is not nil as well. The request is done on the main-thread according to my debugger. Anything else I should check?!
Also, if I quit the view and come back, the images won't be downloaded again and the "Already" log will appear. However, if I close and reopen the app, they will have to be redownloaded, which is weird because the rest of the CoreData is still present.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Master"];
Update #2
It appears that all my ManagedObjectContext are the same. Could it have to do with the cache?

Answer 1

First thing to check, is plant or plant.picture nil after fetch? Second, you say that the request is made on the main thread and that your context is not nil. However, the response(inside the block) is it on the main thread? From the code you shared I would say plant.picture is nil, but other things are possible too.

Answer 2

You need to make sure that pictureData should have type transformable
And also in your class you need pictureData to be id not NSData
Like this
#property (nonatomic, retain) id pictureData;