iOS - Download file only if modified (NSURL & NSData)

Question

I am downloading a bunch of image files from a server, and I want to ensure that they are downloaded only if they are newer. This method currently downloads the images just

Answer 1

If your server supports HTTP caching you can specify you want cached content with NSURLRequestReloadRevalidatingCacheData:

NSURLRequest* request = [NSURLRequest requestWithURL:thumbnailURL cachePolicy:NSURLRequestReloadRevalidatingCacheData timeoutInterval:20];
NSURLResponse* response;
NSError* error;
NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
UIImage* image = [UIImage imageWithData:data];

For more info read the NSURLRequest documentation.