Retrieving NSImage from CoreData - Mac OS X - macos

Question

I'm trying to add images into core data and load it when needed. I'm currently adding the NSImage to the core data as follows:
Thumbnail *testEntity = (Thumbnail *)[NSEntityDescription insertNewObjectForEntityForName:#"Thumbnail" inManagedObjectContext:self.managedObjectContext];
NSImage *image = rangeImageView.image;
testEntity.fileName = #"test";
testEntity.image = image;
NSError *error;
[self.managedObjectContext save:&error];
Thumbnail is the entity name and I have two attributes under the Thumbnail entity - fileName(NSString) and image (id - transformable).
I'm trying to retreive them as below:
NSManagedObjectContext *context = [self managedObjectContext];
NSFetchRequest * fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *imageEntity = [NSEntityDescription entityForName:#"Thumbnail" inManagedObjectContext:[context valueForKey:#"image"]];
[fetchRequest setEntity:imageEntity];
NSError *error;
NSArray * array = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (array == nil) {
NSLog(#"Testing: No results found");
}else {
_coreDataImageView.image = [array objectAtIndex:0];
}
I end up with this error:
[<NSManagedObjectContext 0x103979f60> valueForUndefinedKey:]: this class is not key value coding-compliant for the key image.
The image is added but couldn't retrieve.
Any idea on how to go about with this? Am I doing it right ?

Answer 1

The error is in this line
NSEntityDescription *imageEntity = [NSEntityDescription entityForName:#"Thumbnail"
inManagedObjectContext:[context valueForKey:#"image"]];
You cannot apply valueForKey:#"image" to a managed object context. You have to apply it to the fetched objects (or use the image property of the fetched object).
Note also that executeFetchRequest: returns nil only if an error occurs. If no entities are found, it returns an empty array.
NSEntityDescription *imageEntity = [NSEntityDescription entityForName:#"Thumbnail" inManagedObjectContext:context];
[fetchRequest setEntity:imageEntity];
NSError *error;
NSArray * array = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
if (array == nil) {
NSLog(#"Testing: Fetch error: %#", error);
} else if ([array count] == 0) {
NSLog(#"Testing: No results found");
}else {
Thumbnail *testEntity = [array objectAtIndex:0];
NSImage *image = testEntity.image;
_coreDataImageView.image = image;
}