Core Data never release NSData loaded from external storage

Question

So I use Core Data to store a few images. (Also the subclass is generated with latest mogenerator)

(And also I'm using ARC)

Yeah I know I could just keep a reference and store it on the disk, but I thought :

"Hey they made an option so I can do just that without having to manage it myself!"

So I tried it and it works perfectly except all the data loaded that way is never released.

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In the initialization of the ViewController who's gonna be in charge of displaying the images I give it the usual main NSManagedObjectContext.

And in a method called in viewDidAppear I set up the UIScrollView with the images :

Edit : So it's not really a fetch request I have an Entity1 which have one-to-many with images and I use it to get the images I get this entity1 from the same context. I just wanted to simplify to explain better.

- (void)setupScrollViewWithEntity1:(Entity1 *)entity1 {
    DDLogVerbose(@"-- %@ : SETUP SCROLL VIEW --", self);
    // I remove any previous subviews
    [self.scrollView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    self.scrollView.contentSize = self.scrollView.frame.size;

    /* Here I get the imagesArray with a NSFetchRequest */ 
    //So it's not really a fetch request I have an `Entity1` which have one-to-many with images and I use it to get the images
    NSSet *imagesSet = entity1.images;


    // So I have an NSArray holding all the Image object
    for (Image *image in imagesSet) {
        CGRect frame = self.scrollView.frame;
        frame.origin.x = image.numberValue*frame.size.width;
        UIScrollView *scrollView = [[UIScrollView alloc]initWithFrame:frame];
        scrollView.contentSize = self.scrollView.frame.size;
        UIImageView *imageView = [[UIImageView alloc]initWithFrame:self.scrollView.frame];
        imageView.image = [UIImage imageWithData:image.image];
        imageView.contentMode = UIViewContentModeScaleAspectFit;
        imageView.userInteractionEnabled = YES;
        [scrollView addSubview:imageView];
        scrollView.delegate = self;
        scrollView.minimumZoomScale = 1.0;
        scrollView.maximumZoomScale = 3.0;
        [self.scrollView addSubview:scrollView];
    }
}

}

In viewWillDisappear I save the NSManagedObjectContext and I would expect when the controller gets dealloc'ed that all the data would too, but it stays in memory forever.

This Line somehow retains it don't know why : imageView.image = [UIImage imageWithData:image.image];

I spent 3 days on it trying to use everything, Instruments, rechecked if I didn't keep a strong reference somewhere.

The thing is the UIViewController gets dealloc'ed that I'm sure of, I see it in Instruments with the Allocation tool but for some reason the data stays in memory forever until the app crashes.

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Here's the list of the ~20 images in memory not getting dealloc'ed :

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And here's the details for the first object :

Thank you for reading until here, I'm really desperate :(

Answer 1

Have you tried calling reset on the NSManagedObjectContext after you are done with the images? That evicts any loaded objects from the in-memory object graph. They will then need to be fetched from disk/db next time they are required.