Save and Retrieve of an UIImage on CoreData

In my app, I am trying to save and retrieval of an image in core data. I am able to save an image successfully after convention of UIimage into NSData, But when I am trying to get an image as NSData it shows output as given below,

case 1: When trying to display as a string from DB.

 <Event: 0x5b5d610> (entity: Event; id: 0x5b5ce30 <x-coredata://F51BBF1D-6484-4EB6-8583-147E23D9FF7B/Event/p1> ; data: <fault>)

case 2: When trying to display as Data

 [Event length]: unrecognized selector sent to instance 0x5b3a9c0
 2010-07-28 19:11:59.610 IMG_REF[10787:207] *** Terminating app due to uncaught exception    'NSInvalidArgumentException', reason: '-[Event length]: unrecognized selector sent to instance 0x5b3a9c0'

My code,

to save:

NSManagedObjectContext *context = [self managedObjectContext];

newsObj = [NSEntityDescription insertNewObjectForEntityForName:@"Event" inManagedObjectContext:context];

NSURL *url = [NSURL URLWithString:@"http://www.cimgf.com/images/photo.PNG"];

NSData *data = [[NSData alloc] initWithContentsOfURL:url];

uiImage = [UIImage imageWithData:data];

NSData * imageData = UIImagePNGRepresentation(uiImage);

[newsObj setValue:imageData forKey:@"imgPng"];

NSError *error;

@try{

    if (managedObjectContext != nil) {

        if (![managedObjectContext save:&error]) {

            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);

            NSString * infoString = [NSString stringWithFormat:@"Please check your connection and try again."];

            UIAlertView * infoAlert = [[UIAlertView alloc] initWithTitle:@"Database Connection Error" message:infoString delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];

            [infoAlert show];

            [infoAlert release];
        } 
    }

}@catch (NSException *exception) {

    NSLog(@"inside exception");
}

to retrieve,

    NSMa


                    
                    
                        
                        iphone
                        
                        objective-c
                        
                        core-data
                        
                        uiimage
                        
                        save
                        
                    
                    
                        
                        
                        
                        
                        
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When you retrieve the image, you're performing the fetch request and storing the results in the variable array, meaning array holds an NSArray of Event objects. Then, later, you assign:

dataBytes = [array objectAtIndex:0];

This means that dataBytes, which you declared as NSData, is now actually an instance of Event. Then when you go to initialize the image, part of the implementation of imageWithData: calls length on what it expects to be your NSData object, but is actually an Event object, hence the error message.

You should adjust your code to read:

dataBytes = [[array objectAtIndex:0] imgPng];

That way, you're getting the first Event object out of the array, then fetching its imgPng property (an instance of NSData, which is what you want).

As a side note, your declaration of dataBytes using the alloc-init on the line above may be extraneous, since you change dataBytes to be the data from your Event immediately afterwards.

answered 2010-07-28T13:51:49.623

Save and Retrieve of an UIImage on CoreData

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