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PONSOperationQueue and threads problem
 

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    <p>Well I have a serious problem. I have a class that manages connections with NSOperationQueue and delegate methods for that class that are actually NSURLConnection delegate methods. Sometimes, I have to pop the viewController that has the answer of my delegate class but it gets trapped in the scope of the delegate function, populating a UITableView and the app crashes just there. I solved it using @synchronized on the viewController dealloc and on the NSURLConnection delegates, but I don't think is the cleanest way since UI freezes sometimes when I'm adding a lot of info to the tableView. So, is there a way to do this clean?</p> <pre><code>- (void)viewDidLoad:(BOOL)animated { [myManager startRequest]; } //myManager class callback - (void)managerDelegate { //Doing things and just poped the viewController while in the function scope //Program crashes, most of logs are "UIViewController message sent to deallocated instance" } //viewController dealloc - (void)dealloc { @synchronized([Manager class]) { alert.delegate = nil; searchResultsTableView.delegate = nil; searchResultsTableView.dataSource = nil; [searchResultsTableView release]; searchResultsTableView = nil; [serviceSearch release]; serviceSearch = nil; [searchResults release]; searchResults = nil; [XMLTag release]; XMLTag = nil; [XMLParserServicesKeys release]; XMLParserServicesKeys = nil; [XMLParserKeys release]; XMLParserKeys = nil; [searchString release]; searchString = nil; [__managedObjectContext release]; __managedObjectContext = nil; manager.delegate = nil; [manager stopAllRequests]; [manager release]; manager = nil; [super dealloc]; } } </code></pre> <p>Edit: some more code, now of myManager class</p> <pre><code>- (void) stopAllRequests { #ifdef _WSMANAGER_DEBUG_ NSLog(@"stopAllRequests %d", [connectionsArray count]); #endif [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO]; for(NNSURLConnection* connection in connectionsArray) { [connection cancel]; [connection release]; } [connectionsArray removeAllObjects]; [queue cancelAllOperations]; } - (BOOL)startRequest { //Data initialization NSInvocationOperation* operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(beginConnection:) object:[NSDictionary dictionaryWithObjectsAndKeys:request, kRequestKey, keyInfo, kUserInfoKey, nil]]; [queue addOperation:operation]; [operation release]; return YES; } -(void) beginConnection:(id)object { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NNSURLConnection* connection = [[NNSURLConnection alloc] initWithRequest:[object objectForKey:kRequestKey] delegate:self]; if(connection) { NSMutableData *requestData = [[NSMutableData alloc] init]; connection.url = [((NSURLRequest*)[object objectForKey:kRequestKey]) URL]; connection.userInfo = [NSDictionary dictionaryWithObjectsAndKeys:[object objectForKey:kUserInfoKey], kUserInfoKey, requestData, kRequestDataKey, nil]; [connectionsArray addObject:connection]; [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES]; } [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:TIMEOUT]]; if([connectionsArray indexOfObject:connection] != NSNotFound) { [connection cancel]; if([delegate conformsToProtocol:@protocol(ManagerDelegate)] &amp;&amp; [delegate respondsToSelector:@selector(managerFailed:withKey:errorCode:)]) { [delegate managerFailed:self withKey:[connection.userInfo objectForKey:kUserInfoKey] errorCode:ManagerErrorCodeTimeout]; if([connectionsArray count] &lt; 1) [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO]; } [connectionsArray removeObject:connection]; } [pool drain]; } - (void)connectionDidFinishLoading:(NNSURLConnection *)connection { @synchronized([Manager class]) { NSMutableData *requestData = [connection.userInfo objectForKey:kRequestDataKey]; NSString* responseString = [[NSString alloc] initWithData:requestData encoding:NSUTF8StringEncoding]; if([delegate conformsToProtocol:@protocol(PLMWSManagerDelegate)] &amp;&amp; [delegate respondsToSelector:@selector(managerSuccess:responseString:withKey:)]) [delegate managerSuccess:self responseString:responseString withKey:[connection.userInfo objectForKey:kUserInfoKey]]; [responseString release]; [requestData release]; [connectionsArray removeObject:connection]; [connection cancel]; [connection release]; connection = nil; if([connectionsArray count] &lt; 1) [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO]; } } </code></pre>
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    1. COThis seems like a strange way around of doing things. Instead of creating and responding to connections on the main thread you seem to be running them synchronously (but not by their synchronous interface, instead by giving each a dedicated run loop) and via an operation queue so that they don't interrupt the main thread. Is there a reason you don't run them by their built-in asynchronous on the main run loop?
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    2. COI think it is asynchronous since every call to startRequest creates its operation and it is ran by the current operation thread shown on the [NSRunLoop currentLoop] isn't it? Or how do you say it could be done on the main thread runLoop?
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    3. COSorry, my fault, I was being far too loose with the semantics. I considered your use to be synchronous because the thread that makes the request will block until the request is complete. Obviously it's asynchronous from the perspective of the main thread, since that posts the operation then goes about its business and waits to hear back. I'll edit my answer to add information about NSURLConnections on the main run loop.
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