iPhone: Handle two(or multiple) responses for two requests in the same delegate - iphone

Question

I am calling NSURLConnection asynchronous method calls in my view controller. I would like to handle TWO RESPONSES FOR TWO REQUEST in the same Delegate. Please suggest me what would the best approach to achieve this? I'm developing in iOS 5 SDK.
UPDATED:
// Class A
[serverconns setDelegate:self];
connection = [serverconns executeAsyncHttpPost :firstjsonrequest];
[serverconns setDelegate:self];
connection = [serverconns executeAsyncHttpPost :secondjsonrequest];
- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
}
- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[self.appendData appendData:data];
}
- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
// logs the error
}
- (void) connectionDidFinishLoading:(NSURLConnection *)connection
{
NSData *responseData = [[NSData alloc] initWithData:appendData];
//HOW CAN WE HANDLE TWO RESPONSES FOR TWO REQUEST in the same Delegate
if (responseData)
{
// doing something
}
}
//Class B: ServerConnection
- (NSURLConnection *) executeAsyncHttpPost :(id) jsonParams
{
NSString *urlstr = [NSString stringWithFormat:#"%#", baseURL];
urlstr = [urlstr stringByAppendingFormat:method];
NSURL *pUrl = [NSURL URLWithString:urlstr];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:pUrl];
NSData *requestData = [NSData dataWithBytes:[jsonParams UTF8String] length:[jsonParams length]];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[request setHTTPBody: requestData];
return [[NSURLConnection alloc] initWithRequest:request delegate:delegateResponder startImmediately:YES];
}
-(void) setDelegate:(id)newDelegate
{
delegateResponder = newDelegate;
}

Answer 1

save your connections somewhere (maybe ivar of your delegate)
- (void) connectionDidFinishLoading:(NSURLConnection *)connection
{
NSData *responseData = [[NSData alloc] initWithData:appendData];
//HOW CAN WE HANDLE TWO RESPONSES FOR TWO REQUEST in the same Delegate
if (responseData)
{
if (connection == yourFirstConnection) {
// doing something for first connection
} else {
// doing something for second connection
}
}
}
just point out some minor problem of your code
NSString *urlstr = [NSString stringWithFormat:#"%#", baseURL];
urlstr = [urlstr stringByAppendingFormat:method];
should replace to
NSString *urlstr = [baseURL absoluteString];
urlstr = [urlstr stringByAppendingString:method];
and add two(or more or array) weak/assign property of NSURLConnection to your class A (connection delegate)
#property (assign) NSURLConnection *myFirstConnection;
#property (assign) NSURLConnection *mySecondConnection;
// assume only need to handle two connection otherwise NSArray should be used instead
than in your class B (create connection)
- (NSURLConnection *) executeAsyncHttpPost :(id) jsonParams
{
NSString *urlstr = [baseURL absoluteString];
urlstr = [urlstr stringByAppendingString:method];
NSURL *pUrl = [NSURL URLWithString:urlstr];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:pUrl];
NSData *requestData = [NSData dataWithBytes:[jsonParams UTF8String] length:[jsonParams length]];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[request setHTTPBody: requestData];
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:delegateResponder startImmediately:YES];
delegateResponder.myFirstConnection = connection;
// delegateResponder.mSecondConnection = connection;
return connection;
}

Answer 2

If I were you I would create a CustomClass which inherits the NSURLConnection. And I will add property called tag.
When I initiate the CustomClass, I would set the tag property and use that to determine which request is being worked on
CustomURLConnection *connection = [[CustomURLConnection alloc] initWithRequest:request delegate:self tag:1];
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate tag:(int)_tag
{
if(self = [super initWithRequest:request delegate:delegate])
{
self.tag = _tag;
}
Now in the code you posted add this
- (void) connectionDidFinishLoading:(NSURLConnection *)connection
{
NSData *responseData = [[NSData alloc] initWithData:appendData];
//HOW CAN WE HANDLE TWO RESPONSES FOR TWO REQUEST in the same Delegate
if (responseData)
{
if (connection.tag == 1){
}
}
}
return self;
}

Answer 3

I think all the mentioned solutions are "ugly". I would not implement a solution with delegate methods but instead create a blocks-based solution. I could post an example if you're interested. I would make use of the AFNetworking classes for this approach.
What follows is an example of a class that handles 2 different responses without using a delegate implementation, opting for blocks instead with the AFNetworking library.
- (void)JSONFromService
{
// create the first request and set the methods that handle the return values (either NSData or NSError in this case) in blocks ...
NSURL *firstURL = [NSURL URLWithString:#"http://dl.dropbox.com/u/6487838/test1.html"];
NSURLRequest *firstRequest = [NSURLRequest requestWithURL:firstURL];
AFHTTPRequestOperation *firstOperation = [[AFHTTPRequestOperation alloc] initWithRequest:firstRequest];
[firstOperation setCompletionBlockWithSuccess:^ (AFHTTPRequestOperation *operation, id object)
{
NSString *firstString = [[NSString alloc] initWithData:object encoding:NSASCIIStringEncoding];
NSLog(#"%#", firstString);
} failure:^ (AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"%#", error);
}];
[firstOperation start];
// create the second request and set the methods that handle the return values (either NSData or NSError in this case) in blocks ...
NSURL *secondURL = [NSURL URLWithString:#"http://dl.dropbox.com/u/6487838/test2.html"];
NSURLRequest *secondRequest = [NSURLRequest requestWithURL:secondURL];
AFHTTPRequestOperation *secondOperation = [[AFHTTPRequestOperation alloc] initWithRequest:secondRequest];
[secondOperation setCompletionBlockWithSuccess:^ (AFHTTPRequestOperation *operation, id object) {
NSString *secondString = [[NSString alloc] initWithData:object encoding:NSASCIIStringEncoding];
NSLog(#"%#", secondString);
} failure:^ (AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"%#", error);
}];
[secondOperation start];
}

Answer 4

I usually subclass NSURLConnection and add properties to store whatever context I need to handle the response.
Since the delegate methods get NSURLConnection passed in, you can just cast it back to your subclass and access the context.
Take a look at this example.

Answer 5

I think you should keep all of your connections in an activeConnections array. Every time one finishes, you do [activeConnections indexForObject:connection] and you update your delegate method accordingly, using the index.
Now, a cleaner way to do it( and a better way from my point of view, but this depends on how large is the data you want to transfer) is to use queues. I'll provide a small example and add comments to it:
// we assume you have 2 requests: req1, req2
//now, create a new dispatch queue
dispatch_queue_t netQueue = dispatch_queue_create("com.mycompany.netqueue",DISPATCH_QUEUE_SERIAL);
//execute the operations in the queue ASYNC
//is very important to dispatch this ASYNC on a background thread, otherwise your UI will be stuck until the request finishes
dispatch_async(netQueue,
^{
// We are on a background thread, so we won't block UI events (or, generally, the main run loop)
NSHTTPURLResponse *response = nil;
NSError *error = nil;
NSData *data = nil;
//We can call the request synchronous and block this thread until completed
data = [NSURLConnection sendSynchronousRequest:req1
returningResponse:&response
error:&error];
dispatch_async(dispatch_get_main_queue(),
^{
//call your delegate with the appropriate method for req1
//be sure to copy the contents in data, as we will reuse it with the next request
});
//We can call the other request synchronous and block this thread until completed
data = [NSURLConnection sendSynchronousRequest:req2
returningResponse:&response
error:&error];
dispatch_async(dispatch_get_main_queue(),
^{
//call your delegate with the appropriate method for req2
});
//and this can go on forever. If you have many requests to execute, simply put them in a loop
});
dispatch_release(netQueue);