Caching the downloaded data

Question

I am using collection View to display the product data in each cell. Each time when user refreshes collectionview , it fetches data from the server again.

I need to know is there a caching mechanism available which caches downloaded images. I want to download only recently updated products which are not cached.

NSURL *url = [NSURL URLWithString:@"http://www.myURL/productAll.php"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
    NSError *myError = nil;
    id res = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&myError];        
    items = [[NSMutableArray alloc] init];
    for (int i=0; i<[res count]; i++) {
        NSString *arrayResult = [[res objectAtIndex:i]objectForKey:@"image"];            
        NSData *data = [[NSData alloc] initWithBase64EncodedString:arrayResult options:NSDataBase64DecodingIgnoreUnknownCharacters];
        UIImage *captcha_image = [[UIImage alloc] initWithData:data];
        [items addObject:captcha_image];
    }
    [collectionView reloadData];
}];

Answer 1

Use NSURLCache to setup memory and disk cache like this:

int cacheSizeMemory = xxxxx; //in memory cache
int cacheSizeDisk = xxxxx; //disk cache
NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:cacheSizeMemory diskCapacity:cacheSizeDisk diskPath:@"nsurlcache"];
[NSURLCache setSharedURLCache:sharedCache];