Question

I have the worst internet connection atm, so sorry if this has been asked before..

I have an NSURLConnection for getting some json data. Until now it worked perfectly fine to use the delegate method didReceiveData:(NSData*)data to save the received data. I am downloading data from at least seven different pages at the same time. Today, after updati g on of the json-pages to contain more data, the NSData object seemed corrupt. I have recently been told that this delegate does not return the whole data, and thus corrupting my information.

Is there another delegate like the didFinish only it also returns the full complete object? Or do I have to do this myself, like merging two NSData’s?

Sorry for stupidity, and grammatical errors are dedicated to iPhone auto-correct.

Answer 1

You must never, ever rely on didReceiveData: returning the full data, because it will break one day. You have to collect your chunks of data in an NSMutableData:

NSMutableData *d = [[NSMutableData alloc] init];

- (void)connection:(NSURLConnection *)c didReceiveData:(NSData *)data
{
    [d appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)conn
{
    // 'd' now contains the entire data
}

If it’s inconvenient for you, you can avoid using NSURLConnection and use a background thread to grab the data in one piece using:

NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://web.service/response.json"]];