Multiple NSURLCoonections in same View using iphone sdk

Question

Can any one of you post the code snippet, example tutorial on handling the multiple

NSURLConnections from the same viewController using cocoa Touch framework....

Thanks for all your future help.....

Answer 1

See this link for the answer. It wraps nsurlconnection with asihttp, which makes your life much easier.

Does ASIHTTP support multi threads?

Answer 2

I handled multiple NSUrlConnections using a NSMutableDictionary which keeps track of which instance of NSMutableData a particular NSURLConnection should save its result to.

At the beginning of my class I define:

NSMutableDictionary *dataDictionary;

Then in my loadData method, I have:

        // Create the request
    NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:currentCam]
                                              cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                          timeoutInterval:30];

    // create the connection with the request
    // and start loading the data
    NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    if (theConnection) {

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

        //keep track of this connection by adding it to subViewDictionary and dataDictionary with appropriate objects.
        [dataDictionary setObject:receivedData forKey:[theConnection description]];
    } 

    else {

        NSLog(@"ERROR DOWNLOADING WITH NSURLCONNECTION");
    }

    [theConnection release];

I use [theConnection description] as my key and an instance of MSMutableData as the object in my dictionary, so later I can look up which instance goes with a particular connection. If you fail to do this you can have issues with data corruption (multiple connections can all save their data to the same variable).

Then, I define the following NSURlConnection delegate methods:

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSMutableData *)data
{
    //look up in dictionary to find out which recievedData instance to use.
    NSMutableData *theReceivedData = [dataDictionary objectForKey:[connection description]];

    // Append the new data to receivedData.
    [theReceivedData appendData:data];
}


- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
        //Lookup in the dictionary to find the correct instance of recievedData to put image into.  
    NSMutableData *theReceivedData = [dataDictionary objectForKey:[connection description]];
    [theReceivedData setLength:0];
    [activityIndicator stopAnimating];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    // inform the user that there was an error
    NSLog(@"Connection failed! Error - localizedDescription:%@ NSURLErrorFailingURLStringErrorKey:%@",
          [error localizedDescription],
          [[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);


    NSMutableData *theReceivedData = [dataDictionary objectForKey:[connection description]];
    [theReceivedData release];

    //remove keys for this connection since it did not load.
    [dataDictionary removeObjectForKey:[connection description]];   
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{

    //look up correct instance of recievedData in teh dictionary for this connection
    NSMutableData *theReceivedData = [dataDictionary objectForKey:[connection description]];

    NSLog(@"Succeeded! Received %d bytes of data",[theReceivedData length]);

    //---do stuff with data here//  

    [theReceivedData release];
}

There is a good tutorial on NSURlConnection here for a single connection. My code is based on that with the addition of the NSMutableDictionary to keep track of each NSUrlConnection and each NSMutableData instance.

I hope that makes sense and is helpful!