Application getting crashed in the NSURLConnection

Question

I am trying to post a URL to the server using the Asynchronous type like

_urlConn = [[NSURLConnection alloc] initWithRequest:_urlReq delegate: self];

I getting proper response, and I am handling the response well using the delegate methods such as didRecieveResponse and connectionDidFinishLoading. The flow works fine as of now. I am facing a new problem which I couldn't figure it out clearly.

Lets say I am having a button which will post the same URL.

I am clicking button to post the url
When the button is clcked again(within one/two sec), the URL is not posted (I have written logic).
The URL is posted(For the fist button click) and I didn't received any response till now, now I am trying to click the button again which will post the URL now.

My app getting exactly right here. Is it because I am using the _ReleaseObject(_urlConn); in the connectionDidFinishLoading method ????

score 1 · Accepted Answer · answered Jun 18 '12 at 14:32

You need to be very careful when working with delegate callbacks.

In this example, a single object is the delegate for two simultaneous NSURLConnection objects. This is a bad idea. Unless you develop a way of associating a specific connection with the appropriate response data object, you will end up mixing response data. In this case you make things worse for yourself by using _urlConn (an iVar i assume) instead of connection (the parameter passed to -connectionDidFinishLoading:).

To simplify all of this, you need to either not make a new request when an existing request is pending, or you need to cancel the old request before you start a new request.

score 1 · Answer 2 · edited May 23 '17 at 11:49

I just answered somebody's question here about handling multiple concurrent downloads with the same delegate. (@Jeffery is right - it needs to keep state for each, keyed on the connection object).

Here's how I'd handle your specific example...

- (IBAction)postButtonPressed:(id)sender {

    sender.enabled = NO;  // no more presses until we are ready again

    [UIView animateWithDuration:0.3 animations:^{
        sender.alpha = 0.3;  // or some effect to make your button appear disabled
    }];

    NSURLRequest *request = // build your post request here

    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue]
        completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

            // check for error, do whatever you intend with the response
            // then re-enable the button
            sender.enabled = YES;
            [UIView animateWithDuration:0.3 animations:^{sender.alpha=1.0;}];
    }];
}

Is NSOperation the way to go right now for Async URL Connections, and we should not be using NSURLConnection delegate methods anymore? — David Cespedes, Mar 13 '13 at 14:12
Both call patterns are here to stay as far as I know, and both are fronting a threaded operation that NSURLConnection performs. The block is prettier, because the completion code and it's context are all in one place. The delegate methods are still needed by some who deal with more complex transactions, like auth challenges, or who want to show incremental progress as bytes flow, etc. — danh, Mar 13 '13 at 20:04

Application getting crashed in the NSURLConnection

2 Answers2