Question

I’m loading certain images from a certain server asynchronously. I’m firing a number of requests at once using NSURLConnection connectionWithRequest method and receive the data using NSURLConnectionDelegate didReceiveData.

At didReceiveData, how do I know which request this data matches? At didReceiveResponse I can use the URL method of the response given as a parameter, but in didReceiveData I only have the received data.

It seemed like the perfect answer would be to use NSURLConnection sendAsynchronousRequest, as the completion handler has all the required parameters: (NSURLResponse*, NSData*, NSError*). I can use [response URL] to make a match to the original request… except in one case: not all the images I try to download exist. In that case, the request is redirected to a generic error page and the URL of that generic page is received, so I can’t match the response to a request I’ve made. This I could handle with connectionWithRequest, but I can’t get the best of both worlds.

Answer 1

In

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

you can use

NSURLRequest *request = [connection originalRequest];

to get the request that the connection was started with.

(This method is available since iOS 5.0, but I could not find it in my Xcode iOS 5.1 Library. You find it in the iOS 6 Library, in the header file NSURLConnection.h or here: http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSURLConnection_Class/Reference/Reference.html#//apple_ref/occ/instm/NSURLConnection/originalRequest).

More methods to manage multiple connections can be found in this thread: Managing multiple asynchronous NSURLConnection connections.

If you use sendAsynchronousRequest:queue:completionHandler: then you can just use the request parameter in the completion block.