CODEWITHSUNDEEP
objective-cconnectionnsmutableurlrequest
Vinicius Albino
Vinicius Albino

Reputation: 763

Cancel NSURLConnection Objective-C

I have a tableviewapplication, wich when the user select one view it needs to parse some XML to display information.But sometimes the XML is not finished downloading and the user can press the button to select the other view,generating a crash.I think i need to cancel the connection or something to dont cause any conflitct with the new connection,but i dont know exactly how,it suppose to be in ViewWillDisappear correct? Heres how i start the connection on ViewDidAppear:

NSMutableURLRequest * req = [[NSMutableURLRequest alloc]initWithURL:[NSURL URLWithString:@"http://Adress"]
                                                        cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:20.0f];

conn = [NSURLConnection connectionWithRequest:req delegate:self];

[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

if(conn)
{
    receivedData = [[NSMutableData alloc]init];
    [DSBezelActivityView newActivityViewForView:self.view withLabel:@"Loading..."];
}


- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    if(conn) [conn cancel];
}

Upvotes: 1

Views: 5507

Answers (2)

Kartihkraj Duraisamy
Kartihkraj Duraisamy

Reputation: 3221

Absolutely you can cancel NSURLConnection.

But you should be careful in cancelling it too.

If you decide to cancel it in viewWillDisappear,

then

You should not do,

autorelease

and also you should not,

release it anywhere.

Here below the brief explaination:

Do cancel your NSURLConnection delegate in viewWillDisappear

[nsurlconnection cancel];

and also you should release it here not anywhere,

[nsurlconnection release];

If you release the connection in somewhere like after your xml response received then,

It will call the viewWillDisappear method anyway,

here you are cancelling it , then it will lead your app to crash.

"deallocated objects will not be cancelled"

.

And also another situation will occurs while cancelling,

If user comes and immediately navigates other view first time, your nsurlconnection will be cancelled in viewWillDisappear method.

Again the user comes to the view and escapes immediately before your nsurlconnection initialized or allocated, also your app will be crashed because,

"deallocated objects will not be cancelled".

So, check your connection != nil before you cancel it and also don't forgot to do 

nsurlconnection = nil;

in the same time.

So that you can avoid the immediate calls [nsurlconnection cancel] crashes.

SO Finally , in your viewWillDisappear method you have to do is,

  1. Need to check nsurlconnection != nil
  2. Need to cancel it
  3. Need to allocate null to your nsurlconnection
  4. Need to release it in the same method.

Sample code will be like the following,

- (void) viewWillDisappear:(BOOL)animated
{

if (nsurlconnection != nil)
{
[nsurlconnection cancel];
[nsurlconnection release];
nsurlconnection = nil;
}

}

Hope it's helpful... Happy coding ...

Upvotes: 2

Tim Dean
Tim Dean

Reputation: 8292

You can call NSURLConnection's cancel method and it will prevent your connections delegate from being called with any more data. You could do this in viewWillDisappear if that's when it makes sense given how your app works.

Upvotes: 3

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