Obj-C, how to stop NSURLConnection behind NSData? - objective-c

Question

how can I stop NSURLConnection behind NSURLConnection ?
code:
NSData *sendreq = [NSURLConnection sendSynchronousRequest:urlreq returningResponse:nil error:nil];
NSString *responseStr =[[NSString alloc] initWithBytes:[sendreq bytes] length:[sendreq length] encoding:NSUTF8StringEncoding];
I use the NSData to store the response from my server, but in this way I cant use "[sendreq cancel]"
so if the NSURLConnection is making a long connection and the user is go to anther VC I want to stop the NSURLConnection, so how can I do it ?

Answer 1

If you want to be able to cancel your request, do not use sendSynchronousRequest, but instead use the asynchronous, delegate-based rendition NSURLConnection. (Frankly, you should avoid using synchronous requests, from the main thread at least, for a variety of reasons.) If you use the delegate-based rendition, you can then call NSURLConnection method cancel when needed.
So, define properties to hold the data and connection reference:
#property (nonatomic, strong) NSMutableData *responseData;
#property (nonatomic, weak) NSURLConnection *connection;
Then start the connection:
self.responseData = [NSMutableData data];
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:urlreq delegate:self];
self.connection = connection;
You obviously have to implement the NSURLConnectionDataDelegate methods:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[self.responseData appendData:data];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSString *responseStr = [[NSString alloc] initWithData:self.responseData encoding:NSUTF8StringEncoding];
// you can use `responseStr` here
// now that we're done with `responseData`, we might want to release it
self.responseData = nil;
}
You want to detect/handle errors, too, with the NSURLConnectionDelegate method:
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
// do whatever you want when error occurs
NSLog(#"%s: %#", __FUNCTION__, error);
}
If you need to cancel it, it's
[self.connection cancel];
You could also use AFNetworking, which uses delegate-based NSURLConnection, but keeps you out of the weeds of the implementation.
You can also use the newer NSURLSession which offers block-based renditions that are still can be cancelled. But that depends upon what OS versions you're trying to support.