iOS: Saving A Picture In UIImageView

Question

I have an app that allows the user to choose a picture from their camera roll, and display it in a UIImageView. I usually use this method to save text in text fields, and I assumed that it would work for an image as well, but I'm having some issues with it. There are no errors, but it simply does not save the image.

This is the relevant code I'm using:

.h:

#define kFilename9        @"PGdata.plist"
...
- (NSString *)dataFilePath;

.m:

- (NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(
                                                         NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:kFilename9];
}

- (void)applicationDidEnterBackground:(NSNotification *)notification {
    NSMutableArray *array = [[NSMutableArray alloc] init];
    [array addObject:image.image];

    [array writeToFile:[self dataFilePath] atomically:YES];
}
- (void)viewDidLoad
{
    ...  

    NSString *filePath = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
        image.image = [array objectAtIndex:0];
    }

    UIApplication *app = [UIApplication sharedApplication];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(applicationDidEnterBackground:)
                                                 name:UIApplicationDidEnterBackgroundNotification
                                               object:app];

    [super viewDidLoad];

}

Answer 1

You have to convert the UIImage to a PNG or JPG first, using UImagePNGRepresentation or UIImageJPEGRepresentation. Those function return NSData which you can then write to a file.