cache

- (void)secondAttempt {
    NSCache *memoryCache = [[NSCache alloc] init]; //assume there is a memoryCache for images or videos

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

        NSString *urlString = @"http://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png";

        NSData *downloadedData = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]];

        if (downloadedData) {

            // STORE IN FILESYSTEM
            NSString* cachesDirectory = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
            NSString *file = [cachesDirectory stringByAppendingPathComponent:urlString];
            [downloadedData writeToFile:file atomically:YES];

            // STORE IN MEMORY
            [memoryCache setObject:downloadedData forKey:@"downloadedPic"];
        }

        // NOW YOU CAN CREATE AN AVASSET OR UIIMAGE FROM THE FILE OR DATA
        NSURL *imageURL = [NSURL fileURLWithPath:@"downloadedPic"];
        NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
        UIImage *image = [UIImage imageWithData:imageData];
        [scheduleImage setImage:image];
        });
}