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• Receive data in same order as that of NSOperationQueue

  - by Nishit

  Hi, I have an NSOperationQueue, in which I keep on adding NSOperation objects that hit server and brings data. Is there a way to store the received data in the order in which they were fired? For example, suppose the A, B and C objects are added in NSOperationQueue in the order ABC. Now each of the three A, B and C will bring data in their corresponding threads. I want to store the results in the same order in an array so that the contents of array becomes "Result A", "Result B" and "Result C". Please provide a solution or a direction towards the right answer for this problems. Thanks Guys Basically, I want to design an autosuggest component which brings data from server (same as in google app), and I thought NSOperationQueue to be the best method to implement this. Currently I set the maxConcurrentOperationCount to 1, but I want to set it to more than 1, as data comes from the server very slowly. Please point out the right dolution or direction towards this question. Thanks

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• NSOperationQueue bug with dependencies

  - by Daniel

  I am using NSOperation and NSOperationQueue for performing a sequence of operations, all dependent on each other (2 on 1, 3 on 2, etc...). I set the dependency after I create the operations. I am encountering problems when the queue completes: the program crashes in the _release part of the code, apparently when the NSOperations are getting released. Note that they all get released at the end by the queue, because it is only after the very last one which depends on the second last one, which depends on etc... that they can be released. If I remove any dependency, the code runs fine. If I change waitUntilFinished: to NO, it crashes, if it is YES, it does not. I have isolated the problem to the following code which does not use any of my custom classes. NSOperation by default is a class that does absolutely nothing. Yet, this still crashes when all operations have completed. Therefore, it appears I am not using NSOperationQueue properly but can't see what is wrong. I am running on 10.9 and I have noticed that in general Maverick 10.9 is much more sensitive to these issues than 10.8. I call this method from the main Thread with a Menu item: - (void) testOperations:(id)object { NSOperationQueue* queue = [ [ NSOperationQueue alloc ] init ]; NSMutableArray* array = [ NSMutableArray array ]; for ( int i = 0; i < 10000; i++) [ array addObject: [[[ NSOperation alloc ] init ] autorelease ] ]; for ( int i = 1; i < [ array count ]; i++) [[ array objectAtIndex:i ] addDependency:[array objectAtIndex:i-1]]; // remove this and no crash [ queue addOperations: array waitUntilFinished:NO ]; // Change to YES, no crash [ queue autorelease ]; // or release, it does not make a difference, in fact leaking the memory makes no difference: the code crashes when the queue is removing the NSOperations } This will crash every single time with: bool objc::DenseMapBase , objc_object*, unsigned long, objc::DenseMapInfo, true: (EXC_BAD_ACCESS) The full stack is: #0 0x9104d81b in objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&) () #1 0x910384e3 in _objc_rootReleaseWasZero () #2 0x9104d5d9 in -[NSObject release] () #3 0x99e41224 in CFRelease () #4 0x99e56277 in -[__NSArrayM dealloc] () #5 0x9104d5ef in -[NSObject release] () #6 0x97f62b22 in -[__NSOperationInternal dealloc] () #7 0x9104d5ef in -[NSObject release] () #8 0x97f62ac8 in -[NSOperation dealloc] () #9 0x9104d5ef in -[NSObject release] () #10 0x99e41224 in CFRelease () #11 0x99e56277 in -[__NSArrayM dealloc] () #12 0x9104d5ef in -[NSObject release] () #13 0x97f62b22 in -[__NSOperationInternal dealloc] () #14 0x9104d5ef in -[NSObject release] () #15 0x97f62ac8 in -[NSOperation dealloc] () #16 0x9104d5ef in -[NSObject release] () #17 0x99e41224 in CFRelease () #18 0x99e56277 in -[__NSArrayM dealloc] () #19 0x9104d5ef in -[NSObject release] () #20 0x97f62b22 in -[__NSOperationInternal dealloc] () #21 0x9104d5ef in -[NSObject release] () #22 0x97f62ac8 in -[NSOperation dealloc] () #23 0x9104d5ef in -[NSObject release] () #24 0x99e41224 in CFRelease () #25 0x99e56277 in -[__NSArrayM dealloc] () #26 0x9104d5ef in -[NSObject release] () #27 0x97f62b22 in -[__NSOperationInternal dealloc] () #28 0x9104d5ef in -[NSObject release] () #29 0x97f62ac8 in -[NSOperation dealloc] () #30 0x9104d5ef in -[NSObject release] () #31 0x99e41224 in CFRelease () #32 0x99e56277 in -[__NSArrayM dealloc] () #33 0x9104d5ef in -[NSObject release] () #34 0x97f62b22 in -[__NSOperationInternal dealloc] () #35 0x9104d5ef in -[NSObject release] () #36 0x97f62ac8 in -[NSOperation dealloc] () #37 0x9104d5ef in -[NSObject release] () #38 0x99e41224 in CFRelease () #39 0x99e56277 in -[__NSArrayM dealloc] () #40 0x9104d5ef in -[NSObject release] () #41 0x97f62b22 in -[__NSOperationInternal dealloc] () #42 0x9104d5ef in -[NSObject release] () #43 0x97f62ac8 in -[NSOperation dealloc] () #44 0x9104d5ef in -[NSObject release] () #45 0x99e41224 in CFRelease () #46 0x99e56277 in -[__NSArrayM dealloc] () #47 0x9104d5ef in -[NSObject release] () #48 0x97f62b22 in -[__NSOperationInternal dealloc] () #49 0x9104d5ef in -[NSObject release] () #50 0x97f62ac8 in -[NSOperation dealloc] () #10722 0x9104d5ef in -[NSObject release] () #10723 0x97f62b22 in -[__NSOperationInternal dealloc] () #10724 0x9104d5ef in -[NSObject release] () #10725 0x97f62ac8 in -[NSOperation dealloc] () #10726 0x9104d5ef in -[NSObject release] () #10727 0x99e41224 in CFRelease () #10728 0x99e56277 in -[__NSArrayM dealloc] () #10729 0x9104d5ef in -[NSObject release] () #10730 0x97f62b22 in -[__NSOperationInternal dealloc] () #10731 0x9104d5ef in -[NSObject release] () #10732 0x97f62ac8 in -[NSOperation dealloc] () #10733 0x9104d5ef in -[NSObject release] () #10734 0x99e41224 in CFRelease () #10735 0x99e56277 in -[__NSArrayM dealloc] () #10736 0x9104d5ef in -[NSObject release] () #10737 0x97f62b22 in -[__NSOperationInternal dealloc] () #10738 0x9104d5ef in -[NSObject release] () #10739 0x97f62ac8 in -[NSOperation dealloc] () #10740 0x9104d5ef in -[NSObject release] () #10741 0x99e41224 in CFRelease () #10742 0x99e56277 in -[__NSArrayM dealloc] () #10743 0x9104d5ef in -[NSObject release] () #10744 0x97f62b22 in -[__NSOperationInternal dealloc] () #10745 0x9104d5ef in -[NSObject release] () #10746 0x97f62ac8 in -[NSOperation dealloc] () #10747 0x9104d5ef in -[NSObject release] () #10748 0x99e41224 in CFRelease () #10749 0x99e56277 in -[__NSArrayM dealloc] () #10750 0x9104d5ef in -[NSObject release] () #10751 0x97f62b22 in -[__NSOperationInternal dealloc] () #10752 0x9104d5ef in -[NSObject release] () #10753 0x97f62ac8 in -[NSOperation dealloc] () #10754 0x9104d5ef in -[NSObject release] () #10755 0x99e41224 in CFRelease () #10756 0x99e56277 in -[__NSArrayM dealloc] () #10757 0x9104d5ef in -[NSObject release] () #10758 0x97f62b22 in -[__NSOperationInternal dealloc] () #10759 0x9104d5ef in -[NSObject release] () #10760 0x97f62ac8 in -[NSOperation dealloc] () #10761 0x9104d5ef in -[NSObject release] () #10762 0x99e41224 in CFRelease () #10763 0x99e56277 in -[__NSArrayM dealloc] () #10764 0x9104d5ef in -[NSObject release] () #10765 0x97f62b22 in -[__NSOperationInternal dealloc] () #10766 0x9104d5ef in -[NSObject release] () #10767 0x97f62ac8 in -[NSOperation dealloc] () #10768 0x9104d5ef in -[NSObject release] () #10769 0x99e41224 in CFRelease () #10770 0x99e56277 in -[__NSArrayM dealloc] () #10771 0x9104d5ef in -[NSObject release] () #10772 0x97f62b22 in -[__NSOperationInternal dealloc] () #10773 0x9104d5ef in -[NSObject release] () #10774 0x97f62ac8 in -[NSOperation dealloc] () #10775 0x9104d5ef in -[NSObject release] () #10776 0x99e41224 in CFRelease () #10777 0x99e56277 in -[__NSArrayM dealloc] () #10778 0x9104d5ef in -[NSObject release] () #10779 0x97f62b22 in -[__NSOperationInternal dealloc] () #10780 0x9104d5ef in -[NSObject release] () #10781 0x97f62ac8 in -[NSOperation dealloc] () #10782 0x9104d5ef in -[NSObject release] () #10783 0x99e41224 in CFRelease () #10784 0x99e56277 in -[__NSArrayM dealloc] () #10785 0x9104d5ef in -[NSObject release] () #10786 0x97f62b22 in -[__NSOperationInternal dealloc] () #10787 0x9104d5ef in -[NSObject release] () #10788 0x97f62ac8 in -[NSOperation dealloc] () #10789 0x9104d5ef in -[NSObject release] () #10790 0x99e41224 in CFRelease () #10791 0x99e56277 in -[__NSArrayM dealloc] () #10792 0x9104d5ef in -[NSObject release] () #10793 0x97f62b22 in -[__NSOperationInternal dealloc] () #10794 0x9104d5ef in -[NSObject release] () #10795 0x97f62ac8 in -[NSOperation dealloc] () #10796 0x9104d5ef in -[NSObject release] () #10797 0x99e41224 in CFRelease () #10798 0x99e56277 in -[__NSArrayM dealloc] () #10799 0x9104d5ef in -[NSObject release] () #10800 0x97f62b22 in -[__NSOperationInternal dealloc] () #10801 0x9104d5ef in -[NSObject release] () #10802 0x97f62ac8 in -[NSOperation dealloc] () #10803 0x9104d5ef in -[NSObject release] () #10804 0x99e41224 in CFRelease () #10805 0x99e56277 in -[__NSArrayM dealloc] () #10806 0x9104d5ef in -[NSObject release] () #10807 0x97f62b22 in -[__NSOperationInternal dealloc] () #10808 0x9104d5ef in -[NSObject release] () #10809 0x97f62ac8 in -[NSOperation dealloc] () #10810 0x9104d5ef in -[NSObject release] () #10811 0x99e41224 in CFRelease () #10812 0x99e56277 in -[__NSArrayM dealloc] () #10813 0x9104d5ef in -[NSObject release] () #10814 0x97f62b22 in -[__NSOperationInternal dealloc] () #10815 0x9104d5ef in -[NSObject release] () #10816 0x97f62ac8 in -[NSOperation dealloc] () #10817 0x9104d5ef in -[NSObject release] () #10818 0x99e41224 in CFRelease () #10819 0x99e56277 in -[__NSArrayM dealloc] () #10820 0x9104d5ef in -[NSObject release] () #10821 0x97f62b22 in -[__NSOperationInternal dealloc] () #10822 0x9104d5ef in -[NSObject release] () #10823 0x97f62ac8 in -[NSOperation dealloc] () #10824 0x9104d5ef in -[NSObject release] () #10825 0x99e41224 in CFRelease () #10826 0x99e56277 in -[__NSArrayM dealloc] () #10827 0x9104d5ef in -[NSObject release] () #10828 0x97f62b22 in -[__NSOperationInternal dealloc] () #10829 0x9104d5ef in -[NSObject release] () #10830 0x97f62ac8 in -[NSOperation dealloc] () #10831 0x9104d5ef in -[NSObject release] () #10832 0x99e41224 in CFRelease () #10833 0x99e56277 in -[__NSArrayM dealloc] () #10834 0x9104d5ef in -[NSObject release] () #10835 0x97f62b22 in -[__NSOperationInternal dealloc] () #10836 0x9104d5ef in -[NSObject release] () #10837 0x97f62ac8 in -[NSOperation dealloc] () #10838 0x9104d5ef in -[NSObject release] () #10839 0x99e41224 in CFRelease () #10840 0x99e56277 in -[__NSArrayM dealloc] () #10841 0x9104d5ef in -[NSObject release] () #10842 0x97f62b22 in -[__NSOperationInternal dealloc] () #10843 0x9104d5ef in -[NSObject release] () #10844 0x97f62ac8 in -[NSOperation dealloc] () #10845 0x9104d5ef in -[NSObject release] () #10846 0x99e41224 in CFRelease () #10847 0x99e56277 in -[__NSArrayM dealloc] () #10848 0x9104d5ef in -[NSObject release] () #10849 0x97f62b22 in -[__NSOperationInternal dealloc] () #10850 0x9104d5ef in -[NSObject release] () #10851 0x97f62ac8 in -[NSOperation dealloc] () #10852 0x9104d5ef in -[NSObject release] () #10853 0x99e41224 in CFRelease () #10854 0x99e56277 in -[__NSArrayM dealloc] () #10855 0x9104d5ef in -[NSObject release] () #10856 0x97f62b22 in -[__NSOperationInternal dealloc] () #10857 0x9104d5ef in -[NSObject release] () #10858 0x97f62ac8 in -[NSOperation dealloc] () #10859 0x9104d5ef in -[NSObject release] () #10860 0x99e41224 in CFRelease () #10861 0x99e56277 in -[__NSArrayM dealloc] () #10862 0x9104d5ef in -[NSObject release] () #10863 0x97f62b22 in -[__NSOperationInternal dealloc] () #10864 0x9104d5ef in -[NSObject release] () #10865 0x97f62ac8 in -[NSOperation dealloc] () #10866 0x9104d5ef in -[NSObject release] () #10867 0x99e41224 in CFRelease () #10868 0x99e56277 in -[__NSArrayM dealloc] () #10869 0x9104d5ef in -[NSObject release] () #10870 0x97f62b22 in -[__NSOperationInternal dealloc] () #10871 0x9104d5ef in -[NSObject release] () #10872 0x97f62ac8 in -[NSOperation dealloc] () #10873 0x9104d5ef in -[NSObject release] () #10874 0x99e41224 in CFRelease () #10875 0x99e56277 in -[__NSArrayM dealloc] () #10876 0x9104d5ef in -[NSObject release] () #10877 0x97f62b22 in -[__NSOperationInternal dealloc] () #10878 0x9104d5ef in -[NSObject release] () #10879 0x97f62ac8 in -[NSOperation dealloc] () #10880 0x9104d5ef in -[NSObject release] () #10881 0x99e41224 in CFRelease () #10882 0x99e56277 in -[__NSArrayM dealloc] () #10883 0x9104d5ef in -[NSObject release] () #10884 0x97f62b22 in -[__NSOperationInternal dealloc] () #10885 0x9104d5ef in -[NSObject release] () #10886 0x97f62ac8 in -[NSOperation dealloc] () #10887 0x9104d5ef in -[NSObject release] () #10888 0x99e41224 in CFRelease () #10889 0x99e56277 in -[__NSArrayM dealloc] () #10890 0x9104d5ef in -[NSObject release] () #10891 0x97f62b22 in -[__NSOperationInternal dealloc] () #10892 0x9104d5ef in -[NSObject release] () #10893 0x97f62ac8 in -[NSOperation dealloc] () #10894 0x9104d5ef in -[NSObject release] () #10895 0x99e41224 in CFRelease () #10896 0x99e56277 in -[__NSArrayM dealloc] () #10897 0x9104d5ef in -[NSObject release] () #10898 0x97f62b22 in -[__NSOperationInternal dealloc] () #10899 0x9104d5ef in -[NSObject release] () #10900 0x97f62ac8 in -[NSOperation dealloc] () #10901 0x9104d5ef in -[NSObject release] () #10902 0x99e41224 in CFRelease () #10903 0x99e56277 in -[__NSArrayM dealloc] () #10904 0x9104d5ef in -[NSObject release] () #10905 0x97f62b22 in -[__NSOperationInternal dealloc] () #10906 0x9104d5ef in -[NSObject release] () #10907 0x97f62ac8 in -[NSOperation dealloc] () #10908 0x9104d5ef in -[NSObject release] () #10909 0x99e41224 in CFRelease () #10910 0x99e56277 in -[__NSArrayM dealloc] () #10911 0x9104d5ef in -[NSObject release] () #10912 0x97f62b22 in -[__NSOperationInternal dealloc] () #10913 0x9104d5ef in -[NSObject release] () #10914 0x97f62ac8 in -[NSOperation dealloc] () #10915 0x9104d5ef in -[NSObject release] () #10916 0x97f49cca in __NSOQSchedule_f () #10917 0x9c1c9e21 in _dispatch_async_redirect_invoke () #10918 0x9c1c53a6 in _dispatch_client_callout () #10919 0x9c1c7467 in _dispatch_root_queue_drain () #10920 0x9c1c8732 in _dispatch_worker_thread2 () #10921 0x960c2dab in _pthread_wqthread () The full crash context is (bold for crash line): libobjc.A.dylib`objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&): 0x9104d800: pushl %ebp 0x9104d801: movl %esp, %ebp 0x9104d803: pushl %esi 0x9104d804: subl $20, %esp 0x9104d807: leal -8(%ebp), %eax 0x9104d80a: movl %eax, 8(%esp) 0x9104d80e: movl 16(%ebp), %eax 0x9104d811: movl %eax, 4(%esp) 0x9104d815: movl 12(%ebp), %esi 0x9104d818: movl %esi, (%esp) **0x9104d81b: calll 0x9104d9b6 ; bool objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::LookupBucketFor<objc_object*>(objc_object* const&, std::__1::pair<objc_object*, unsigned long> const*&) const** 0x9104d820: movl 12(%esi), %ecx 0x9104d823: shll $3, %ecx 0x9104d826: addl (%esi), %ecx 0x9104d828: movl 8(%ebp), %edx 0x9104d82b: testb %al, %al 0x9104d82d: je 0x9104d836 ; objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&) + 54 0x9104d82f: movl -8(%ebp), %eax 0x9104d832: movl %eax, (%edx) 0x9104d834: jmp 0x9104d838 ; objc::DenseMapBase<objc::DenseMap<objc_object*, unsigned long, true, objc::DenseMapInfo<objc_object*> >, objc_object*, unsigned long, objc::DenseMapInfo<objc_object*>, true>::find(objc_object* const&) + 56 0x9104d836: movl %ecx, (%edx) 0x9104d838: movl %ecx, 4(%edx) 0x9104d83b: addl $20, %esp 0x9104d83e: popl %esi 0x9104d83f: popl %ebp 0x9104d840: ret $4 0x9104d843: nop I tried using a pre-created queue, this makes no difference. Apparently, with dependencies, this code is a problem with XCode 5.0, 32-bit. Edit: In fact, I can isolate the problem much further. An empty Cocoa Application project in XCOde 5.0 on 10.9 with ARC on and a single method will crash. If it does not on your computer, increase 4269 to anything bigger: - (void)applicationDidFinishLaunching:(NSNotification *)aNotification { NSOperationQueue* aQueue = [[ NSOperationQueue alloc ] init ]; NSMutableArray* array = [ NSMutableArray array ]; for ( int i = 0; i < 4269; i++) [ array addObject: [ [NSOperation alloc ] init ]]; for ( int i = 1; i < [ array count ]; i++) [[ array objectAtIndex:i ] addDependency:[array objectAtIndex:i-1]]; [ aQueue addOperations: array waitUntilFinished:NO ]; }

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• iPhone: NSOperationQueue running operations serially

  - by Greg Maletic

  I have a singleton NSOperationQueue that handles all of my network requests. I'm noticing, however, that when I have one particularly long operation running (this particular operation takes at least 25 seconds), my other operations don't run until it completes. maxConcurrentOperationCount is set to NSOperationQueueDefaultMaxConcurrentOperationCount, so I don't believe that's the issue. Any reason why this would be happening? Besides spawning multiple NSOperationQueues (a solution that I'm not sure would work, nor am I sure it's a good idea), what's the best way to fix this problem? Thanks.

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• NSOperation inside NSOperationQueue not being executed

  - by Martin Garcia

  I really need help here. I'm desperate at this point. I have NSOperation that when added to the NSOperationQueue is not being triggered. I added some logging to see the NSOperation status and this is the result: Queue operations count = 1 Queue isSuspended = 0 Operation isCancelled? = 0 Operation isConcurrent? = 0 Operation isFinished? = 0 Operation isExecuted? = 0 Operation isReady? = 1 Operation dependencies? = 0 The code is very simple. Nothing special. LoadingConflictEvents_iPad *loadingEvents = [[LoadingConflictEvents_iPad alloc] initWithNibName:@"LoadingConflictEvents_iPad" bundle:[NSBundle mainBundle]]; loadingEvents.modalPresentationStyle = UIModalPresentationFormSheet; loadingEvents.conflictOpDelegate = self; [self presentModalViewController:loadingEvents animated:NO]; [loadingEvents release]; ConflictEventOperation *operation = [[ConflictEventOperation alloc] initWithParameters:wiLr.formNumber pWI_ID:wiLr.wi_id]; [queue addOperation:operation]; NSLog(@"Queue operations count = %d",[queue operationCount]); NSLog(@"Queue isSuspended = %d",[queue isSuspended]); NSLog(@"Operation isCancelled? = %d",[operation isCancelled]); NSLog(@"Operation isConcurrent? = %d",[operation isConcurrent]); NSLog(@"Operation isFinished? = %d",[operation isFinished]); NSLog(@"Operation isExecuted? = %d",[operation isExecuting]); NSLog(@"Operation isReady? = %d",[operation isReady]); NSLog(@"Operation dependencies? = %d",[[operation dependencies] count]); [operation release]; Now my operation do many things on the main method, but the problem is never being called. The main is never executed. The most weird thing (believe me, I'm not crazy .. yet). If I put a break point in any NSLog line or in the creation of the operation the main method will be called and everything will work perfectly. This have been working fine for a long time. I have been making some changes recently and apparently something screw things up. One of those changes was to upgrade the device to iOS 5.1 SDK (iPad). To add something, I have the iPhone (iOS 5.1) version of this application that use the same NSOperation object. The difference is in the UI only, and everything works fine. Any help will be really appreciated. Regards,

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• NSThread vs. NSOperationQueue vs. ??? on the iPhone

  - by kubi

  Currently I'm using NSThread to cache images in another thread. [NSThread detachNewThreadSelector:@selector(cacheImage:) toTarget:self withObject:image]; Alternatively: [self performSelectorInBackground:@selector(cacheImage:) withObject:image]; Alternatively, I can use an NSOperationQueue NSInvocationOperation *invOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(cacheImage:) object:image]; NSOperationQueue *opQueue = [[NSOperationQueue alloc] init]; [opQueue addOperation:invOperation]; Is there any reason to switch away from NSThread? GCD is a 4th option when it's released for the iPhone, but unless there's a significant performance gain, I'd rather stick with methods that work in most platforms.

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• NSURLSession has NSoperationqueue internally?

  - by JeffWood

  A)If NSURLSession runs task in background in iOS7,Has Apple integrated internally Queue in NSURLSession?How it works in secondary thread and also in App suspended Mode? B)What is the difference between NSURLSession and NSoperationqueue? C)If NSURLSession is the replacement of NSURLCOnnection, Can we integrate NSURLSession into NSOPerationqueue? D)Are both same? E)Can we do the same thing in NSURLSession as in NSoperationQueue? If NSURLSession is the relplacement of NSUrlconnection ,Which one is the best in all situations?What is the future of NSUrlconnection?

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• Synchronous communication using NSOperationQueue

  - by chip_munks

  I am new to Objective C programming. I have created two threads called add and display using the NSInvocationOperation and added it on to the NSOperationQueue. I make the display thread to run first and then run the add thread. The display thread after printing the "Welcome to display" has to wait for the results to print from the add method. So i have set the waitUntilFinished method. Both the Operations are on the same queue. If i use waitUntilFinished for operations on the same queue there may be a situation for deadlock to happen(from apples developer documentation). Is it so? To wait for particular time interval there is a method called waitUntilDate: But if i need to like this wait(min(100,dmax)); let dmax = 20; How to do i wait for these conditions? It would be much helpful if anyone can explain with an example. EDITED: threadss.h ------------ #import <Foundation/Foundation.h> @interface threadss : NSObject { BOOL m_bRunThread; int a,b,c; NSOperationQueue* queue; NSInvocationOperation* operation; NSInvocationOperation* operation1; NSConditionLock* theConditionLock; } -(void)Thread; -(void)add; -(void)display; @end threadss.m ------------ #import "threadss.h" @implementation threadss -(id)init { if (self = [super init]) { queue = [[NSOperationQueue alloc]init]; operation = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(display) object:nil]; operation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(add) object:nil]; theConditionLock = [[NSConditionLock alloc]init]; } return self; } -(void)Thread { m_bRunThread = YES; //[operation addDependency:operation1]; if (m_bRunThread) { [queue addOperation:operation]; } //[operation addDependency:operation1]; [queue addOperation:operation1]; //[self performSelectorOnMainThread:@selector(display) withObject:nil waitUntilDone:YES]; //NSLog(@"I'm going to do the asynchronous communication btwn the threads!!"); //[self add]; //[operation addDependency:self]; sleep(1); [queue release]; [operation release]; //[operation1 release]; } -(void)add { NSLog(@"Going to add a and b!!"); a=1; b=2; c = a + b; NSLog(@"Finished adding!!"); } -(void)display { NSLog(@"Into the display method"); [operation1 waitUntilFinished]; NSLog(@"The Result is:%d",c); } @end main.m ------- #import <Foundation/Foundation.h> #import "threadss.h" int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; threadss* thread = [[threadss alloc]init]; [thread Thread]; [pool drain]; return 0; } This is what i have tried with a sample program. output 2011-06-03 19:40:47.898 threads_NSOperationQueue[3812:1503] Going to add a and b!! 2011-06-03 19:40:47.898 threads_NSOperationQueue[3812:1303] Into the display method 2011-06-03 19:40:47.902 threads_NSOperationQueue[3812:1503] Finished adding!! 2011-06-03 19:40:47.904 threads_NSOperationQueue[3812:1303] The Result is:3 Is the way of invoking the thread is correct. 1.Will there be any deadlock condition? 2.How to do wait(min(100,dmax)) where dmax = 50.

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• iPhone: Memory leak when using NSOperationQueue...

  - by MacTouch

  Hi, I'm sitting here for at least half an hour to find a memory leak in my code. I just replaced an synchronous call to a (touch) method with an asynchronous one using NSOperationQueue. The Leak Inspector reports a memory leak after I did the change to the code. What's wrong with the version using NSOperationQueue? Version without a MemoryLeak -(NSData *)dataForKey:(NSString*)ressourceId_ { NSString *path = [self cachePathForKey:ressourceId_]; // returns an autoreleased NSString* NSString *cacheKey = [self cacheKeyForRessource:ressourceId_]; // returns an autoreleased NSString* NSData *data = [[self memoryCache] valueForKey:cacheKey]; if (!data) { data = [self loadData:path]; // returns an autoreleased NSData* if (data) { [[self memoryCache] setObject:data forKey:cacheKey]; } } [[self touch:path]; return data; } Version with a MemoryLeak (I do not see any) -(NSData *)dataForKey:(NSString*)ressourceId_ { NSString *path = [self cachePathForKey:ressourceId_]; // returns an autoreleased NSString* NSString *cacheKey = [self cacheKeyForRessource:ressourceId_]; // returns an autoreleased NSString* NSData *data = [[self memoryCache] valueForKey:cacheKey]; if (!data) { data = [self loadData:path]; // returns an autoreleased NSData* if (data) { [[self memoryCache] setObject:data forKey:cacheKey]; } } NSInvocationOperation *touchOp = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(touch:) object:path]; [[self operationQueue] addOperation:touchOp]; [touchOp release]; return data; } And of course, the touch method does nothing special too. Just change the date of the file. -(void)touch:(id)path_ { NSString *path = (NSString *)path_ NSFileManager *fm = [NSFileManager defaultManager]; if ([fm fileExistsAtPath:path]) { NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:[NSDate date], NSFileModificationDate, nil]; [fm setAttributes: attributes ofItemAtPath:path error:nil]; } }

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• Get notification when NSOperationQueue finishes all tasks

  - by porneL

  NSOperationQueue has waitUntilAllOperationsAreFinished, but I don't want to wait synchronously for it. I just want to hide progress indicator in UI when queue finishes. What's the best way to accomplish this? I can't send notifications from my NSOperations, because I don't know which one is going to be last, and [queue operations] might not be empty yet (or worse - repopulated) when notification is received.

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• GCD and AppleEvents / NSOperationQueue and AppleScript

  - by mahal tertin

  As i understood, the threads provided by GCD do have a runloop but no source/port. Now i use some of methods that call AppleScripts thru AppleEvents inside an NSOperationQueue. And sometimes my app crashes with following stacktrace. my questions: Usage of AppleScript inside a NSInvocationOperation or NSBlockOperation Usage of AppleEvents inside GCD-Threads do i have to add a source / port to a runloop of a gcd-thread before using AppleEvents? do i have to add a source / port to a runloop of a gcd-thread before using [CATransaction commit]? do i have to add a source / port to a runloop of a gcd-thread before using [NSObject performSelectorAfterDelay...] ? if yes, how? can i simply call CFRunLoopRunInMode(kCFRunLoopDefaultMode, 5.0, false); /// or 30 or the defined timeout of appleevent? .. Thread 9: Dispatch queue: com.apple.root.default-priority 0 libSystem.B.dylib 0x00007fff88276e82 semaphore_wait_signal_trap 10 1 libSystem.B.dylib 0x00007fff8827c3cd pthread_mutex_lock 469 2 com.apple.applescript 0x000000011d3d461f AppleScriptComponent 50 3 com.apple.applescript 0x000000011d3edbcc AGenericCall::Delegate(ComponentInstanceRecord*) 46 4 com.apple.applescript 0x000000011d3ed520 AGenericManager::HandleOSACall(ComponentParameters*) 54 5 com.apple.applescript 0x000000011d3ed4b0 GenericComponent 219 6 com.apple.openscripting 0x00007fff8381c6da OSAExecuteEvent 63 7 com.apple.Foundation 0x00007fff86f320d8 -[NSAppleScript(NSPrivate) _executeAppleEvent:withMode:error:] 161 8 xxx 0x0000000100048af0 -[TCallScript callScript:withArrayOfParameters:] 480 9 xxx 0x0000000100048ffd -[TCallScript callHandler:withParameters:] 477 10 xxx 0x0000000100036032 -[ZFOpenWindowController getSafariItemForCurrentTabForWindow:] 66 11 xxx 0x00000001000346af -[ZFOpenWindowController refreshWindowList:] 1679 12 xxx 0x000000010003541c -[ZFOpenWindowController bringZFToForegroundZoomOut:orJustLinkFrontMost:toItem:] 2988 13 xxx 0x0000000100053556 __-[ZFSelectionTool openWithPreferredApplication:]_block_invoke_516 54 14 com.apple.Foundation 0x00007fff86ed87d9 -[NSBlockOperation main] 140 15 com.apple.Foundation 0x00007fff86ec906d -[__NSOperationInternal start] 681 16 com.apple.Foundation 0x00007fff86ec8d23 ____startOperations_block_invoke_2 99 17 libSystem.B.dylib 0x00007fff882b2ce8 _dispatch_call_block_and_release 15 18 libSystem.B.dylib 0x00007fff88291279 _dispatch_worker_thread2 231 19 libSystem.B.dylib 0x00007fff88290bb8 _pthread_wqthread 353 20 libSystem.B.dylib 0x00007fff88290a55 start_wqthread 13 ... Thread 11 Crashed: Dispatch queue: com.apple.root.default-priority 0 com.apple.applescript 0x000000011d40f658 BCHandleError() 182 1 com.apple.applescript 0x000000011d4059ca UASExecute1() 2546 2 com.apple.applescript 0x000000011d3dd1d5 ASExecuteEvent(AEDesc const*, unsigned int, int, unsigned int*) 695 3 ...ple.CoreServices.CarbonCore 0x00007fff85388e04 CallComponentFunction 28 4 com.apple.applescript 0x000000011d3d4cad AppleScriptComponent 1728 5 com.apple.applescript 0x000000011d3edbcc AGenericCall::Delegate(ComponentInstanceRecord*) 46 6 com.apple.applescript 0x000000011d3ed520 AGenericManager::HandleOSACall(ComponentParameters*) 54 7 com.apple.applescript 0x000000011d3ed4b0 GenericComponent 219 8 com.apple.openscripting 0x00007fff8381c6da OSAExecuteEvent 63 9 com.apple.Foundation 0x00007fff86f320d8 -[NSAppleScript(NSPrivate) _executeAppleEvent:withMode:error:] 161 10 xxx 0x0000000100048af0 -[TCallScript callScript:withArrayOfParameters:] 480 11 xxx 0x0000000100048ffd -[TCallScript callHandler:withParameters:] 477 12 xxx 0x0000000100035c67 -[ZFOpenWindowController getItemForAXDocumentOfFrontMostWindow] 119 13 xxx 0x00000001000359f1 -[ZFOpenWindowController getItemForFrontMostWindow:] 721 14 xxx 0x00000001000348ac -[ZFOpenWindowController bringZFToForegroundZoomOut:orJustLinkFrontMost:toItem:] 60 15 xxx 0x0000000100053556 __-[ZFSelectionTool openWithPreferredApplication:]_block_invoke_516 54 16 com.apple.Foundation 0x00007fff86ed87d9 -[NSBlockOperation main] 140 17 com.apple.Foundation 0x00007fff86ec906d -[__NSOperationInternal start] 681 18 com.apple.Foundation 0x00007fff86ec8d23 ____startOperations_block_invoke_2 99 19 libSystem.B.dylib 0x00007fff882b2ce8 _dispatch_call_block_and_release 15 20 libSystem.B.dylib 0x00007fff88291279 _dispatch_worker_thread2 231 21 libSystem.B.dylib 0x00007fff88290bb8 _pthread_wqthread 353 22 libSystem.B.dylib 0x00007fff88290a55 start_wqthread 13

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• Multiple NSOperationQueues?

  - by Infinity

  Hello! I would like to use NSOperations in my application to resolve threading problems. I have read some tutorials and now I know what I have to do, but I have a problem. There is a must to have the same NSOperationQueue in each class. What if I use a new NSOperationQueue in each class. There will be concurrency problems?

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• NSOperationqueue i want to block main thread

  - by alexeyndru

  i want to block the main thread until something else is done in the background. i used: result=[self performSelectorInBackground:@selector(calculate:) withObject:expression]; just bellow this line I am using result: [self use:result]; i dont want to use result until it is available. to achieve this I implemented calculate: { [[(AppDelegate *)[[UIApplication sharedApplication] delegate] queue] waitUntilAllOperationsAreFinished]; calculating result... } and still, the result is used before it is calculated. so, i didnt block the main thread. pls help me do that. thanks

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• Is it dangerous to set off an autoreleased NSOperationQueue?

  - by Paperflyer

  I have a task that takes a rather long time and should run in the background. According to the documentation, this can be done using an NSOperationQueue. However, I do not want to keep a class-global copy of the NSOperationQueue since I really only use it for that one task. Hence, I just set it to autorelease and hope that it won't get released before the task is done. It works. like this: NSInvocationOperation *theTask = [NSInvocationOperation alloc]; theTask = [theTask initWithTarget:self selector:@selector(doTask:) object:nil]; NSOperationQueue *operationQueue = [[NSOperationQueue new] autorelease]; [operationQueue addOperation:theTask]; [theTask release]; I am kind of worried, though. Is this guaranteed to work? Or might operationQueue get deallocated at some point and take theTask with it?

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• NSOperation unable to load data on the TableView

  - by yeohchan

  I have a problem in NSOperation. I tried many ways but it would run behind the screen, but will not make it appear on the my table view. Can anyone help me out with this. I am new to NSOperation. Recents.h #import <UIKit/UIKit.h> #import "FlickrFetcher.h" @interface Recents : UITableViewController { FlickrFetcher *fetcher; NSString *name; NSData *picture; NSString *picName; NSMutableArray *names; NSMutableArray *pics; NSMutableArray *lists; NSArray *namelists; NSOperationQueue *operationQueue; } @property (nonatomic,retain)NSString *name; @property (nonatomic,retain)NSString *picName; @property (nonatomic,retain)NSData *picture; @property (nonatomic,retain)NSMutableArray *names; @property (nonatomic,retain)NSMutableArray *pics; @property(nonatomic,retain)NSMutableArray *lists; @property(nonatomic,retain)NSArray *namelists; @end Recents.m #import "Recents.h" #import "PersonList.h" #import "PhotoDetail.h" @implementation Recents @synthesize picName,picture,name,names,pics,lists,namelists; // The designated initializer. Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad. - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) { // Custom initialization self.title=@"Recents"; } return self; } - (void)beginLoadingFlickrData{ NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(synchronousLoadFlickrData) object:nil]; [operationQueue addOperation:operation]; [operation release]; } - (void)synchronousLoadFlickrData{ fetcher=[FlickrFetcher sharedInstance]; NSArray *recents=[fetcher recentGeoTaggedPhotos]; [self performSelectorOnMainThread:@selector(didFinishLoadingFlickrDataWithResults:) withObject:recents waitUntilDone:NO]; } - (void)didFinishLoadingFlickrDataWithResults:(NSArray *)recents{ for(NSDictionary *dic in recents){ [names addObject:[fetcher usernameForUserID:[dic objectForKey:@"owner"]]]; if([[dic objectForKey:@"title"]isEqualToString:@""]){ [pics addObject:@"Untitled"]; }else{ [pics addObject:[dic objectForKey:@"title"]]; } NSLog(@"OK!!"); } [self.tableView reloadData]; [self.tableView flashScrollIndicators]; } // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; operationQueue = [[NSOperationQueue alloc] init]; [operationQueue setMaxConcurrentOperationCount:1]; [self beginLoadingFlickrData]; self.tableView.rowHeight = 95; } /* // Override to allow orientations other than the default portrait orientation. - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { // Return YES for supported orientations return (interfaceOrientation == UIInterfaceOrientationPortrait); } */ - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } - (void)dealloc { [super dealloc]; } #pragma mark - #pragma mark Table View Data Source Methods - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return[names count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:SimpleTableIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:SimpleTableIdentifier] autorelease]; } cell.detailTextLabel.text=[names objectAtIndex:indexPath.row]; cell.textLabel.text=[pics objectAtIndex:indexPath.row]; //UIImage *image=[UIImage imageWithData:[self.lists objectAtIndex:indexPath.row]]; //cell.imageView.image=image; return cell; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { fetcher=[[FlickrFetcher alloc]init]; PhotoDetail *scroll=[[PhotoDetail alloc]initWithNibName:@"PhotoDetail" bundle:nil]; scroll.titleName=[self.pics objectAtIndex:indexPath.row]; scroll.picture = [UIImage imageWithData:[self.lists objectAtIndex:indexPath.row]]; [self.navigationController pushViewController:scroll animated:YES]; }

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• Does Multiple NSURLConnection make delay of performance?

  - by oksk

  Hi all~. I made a multi files downloader. I implemented NSURLConnection using NSOperationQueue. NSOpetationQueue has many NSURLConnection operations. and, set MaxConcurrentOperationCount to 10. I thought my code is right, But after run the project, it was wrong. there are some connection error has occured. files url were right. and file download was completed. but downloading files, occur "timed out" error. It is so serious. I tested it with 8 files, and those total size is only 3M. But total download time is 2minutes ~!!! one file download spends only a few second. (2~3 s) but multi files download occur many overburden!! (2 minutes) I don't know why it is... Do Anyone know what reason is?

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• NSInvocationOperation and main thread

  - by kpower

  Imagine that I have a view with some UIKit object as its subview (for example, UIActivityIndicatorView - this doesn't matter). This view also has a selector, called doSomething, which somehow manages UIKit object (in our example it can start or stop indicator view). I create NSInvocationOperation (from view's code parts) with initWithTarget:self selector:@selector(doSomething) object:nil. Then add it to NSOperationQueue. And all works fine. How?! It should be a new thread and non-thread-safe UIKit object! Why no error found (and no crash happened)?

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• I get EXC_BAD_ACCESS when MaxConcurrentOperationCount > 1

  - by kudorgyozo

  Hello i am using NSOperationQueue to download images in the background. I have created a custom NSOperation to download the images. I put the images in table cells. The problem is if I do [operationQueue setMaxConcurrentOperationCount: 10] and i scroll down several cells the program crashes with EXC_BAD_ACCESS. Every time it crashes at the same place in the table. There are 3 cells one after the other which are for the same company and have the same logo so basically it should download the images 3 times. Every other time it works fine. - (void) main { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSURL *url = [[NSURL alloc] initWithString:self.imageURL]; debugLog(@"downloading image: %@", self.imageURL); //NSError *error = nil; NSData *data = [[NSData alloc] initWithContentsOfURL:url]; [url release]; UIImage *image = [[UIImage alloc] initWithData:data]; [data release]; if (image) { if (image.size.width != ICONWIDTH && image.size.height != ICONHEIGHT) { UIImage *resizedImage; CGSize itemSize = CGSizeMake(ICONWIDTH, ICONHEIGHT); UIGraphicsBeginImageContext(itemSize); CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height); [image drawInRect:imageRect]; resizedImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); self.theImage = resizedImage; } else { self.theImage = image; } [image release]; } [delegate didFinishDownloadingImage: self]; [pool release]; } This is how i handle downloading the images. If i comment out [delegate didFinishDownloadingImage: self]; in the function above it doesn't crash but of course it is useless. -(void) didFinishDownloadingImage:(ImageDownloadOperation *) imageDownloader { [self performSelectorOnMainThread: @selector(handleDidFinishDownloadingImage:) withObject: imageDownloader waitUntilDone: FALSE]; } -(void) handleDidFinishDownloadingImage:(ImageDownloadOperation *)imageDownloadOperation { NSArray *visiblePaths = [self.myTableView indexPathsForVisibleRows]; CompanyImgDownloaderState *stateObject = (CompanyImgDownloaderState *)[imageDownloadOperation stateObject]; if ([visiblePaths containsObject: stateObject.indexPath]) { //debugLog(@"didFinishDownloadingImage %@ %@", imageDownloader.theImage); UITableViewCell *cell = [self.myTableView cellForRowAtIndexPath: stateObject.indexPath]; UIImageView *imageView = (UIImageView *)[cell viewWithTag: 1]; if (imageDownloadOperation.theImage) { imageView.image = imageDownloadOperation.theImage; stateObject.company.icon = imageDownloadOperation.theImage; } else { imageView.image = [(TestWebServiceAppDelegate *)[[UIApplication sharedApplication] delegate] getCylexIcon]; stateObject.company.icon = [(TestWebServiceAppDelegate *)[[UIApplication sharedApplication] delegate] getCylexIcon]; } } }

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• nonatomic property in model class when using NSOperationQueue (iPhone)?

  - by Andrew B.

  I have a custom model class with an NSMutableData ivar that will be accessed by custom NSOperation subclasses (using an NSOperationQueue). I think I can guarantee thread-safe access to the ivar from multiple NSOperations by using dependencies, and I can guarantee that I don't access the ivar from other code (say my main app thread) by waiting until the Q has finished all operations. Should I use a nonatomic property specification, or leave it atomic? Is there a significant impact on performance?

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• Perform selector on parent NSOperation

  - by user326943

  I extend NSOperation (call it A) which contains NSOperationQueue for other NSOperations (which is another extended class different from A, call these operations B). When operation A is running (executing B operations) how do i call a specific function/method on operation A when certain event takes place on B operations? For example every operation B that finishes it calls a function on operation A returning itself? *Nested NSOperation and NSOperationQueue(s) Hope this mockup pseudo code can help to draw the picture. //My classes extended from NSOperation NSOperation ClassA NSOperation ClassB //MainApp -(void)applicationDidFinishLaunching:(NSNotification *)aNotification { ClassA A1; ClassA A2; NSOperationQueue Queue; Queue AddOperation: A1; Queue AddOperation: A2; } //Main of ClassA -(void)main { ClassB B1; ClassB B2; NSOperationQueue Queue; Queue AddOperation: B1; Queue AddOperation: B2; } //Main of ClassB -(void)main { //Do some work and when done call selector on ClassA above }

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• Perform selector on paren NSOperation

  - by user326943

  I extend NSOperation (call it A) which contains NSOperationQueue for other NSOperations (which is another extended class different from A, call these operations B). When operation A is running (executing B operations) how do i call a specific function/method on operation A when certain event takes place on B operations? For example every operation B that finishes it calls a function on operation A returning itself? *Nested NSOperation and NSOperationQueue(s) Thanks

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• Textures loaded with NSOperation are blank

  - by Omega

  So I call this method: -(void)beginExecution { NSOperationQueue *queue = [NSOperationQueue new]; NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(execute) object:nil]; [queue addOperation:operation]; [operation release]; } Which triggers this: -(void)execute { [[CCSpriteFrameCache sharedSpriteFrameCache]addSpriteFramesWithFile:@"MyTexture.plist"]; loaded = YES; // This tells me whenever loading is done. } However, when I create a sprite and try to use the texture MyTexture.png, the sprite is a blank canvas. Why is that?

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• iPhone: Does it ever make sense for an object to retain its delegate?

  - by randombits

  According to the rules of memory management in a non garbage collected world, one is not supposed to retain a the calling object in a delegate. Scenario goes like this: I have a class that inherits from UITableViewController and contains a search bar. I run expensive search operations in a secondary thread. This is all done with an NSOperationQueue and subclasses NSOperation instances. I pass the controller as a delegate that adheres to a callback protocol into the NSOperation. There are edge cases when the application crashes because once an item is selected from the UITableViewController, I dismiss it and thus its retain count goes to 0 and dealloc gets invoked on it. The delegate didn't get to send its message in time as the results are being passed at about the same time the dealloc happens. Should I design this differently? Should I call retain on my controller from the delegate to ensure it exists until the NSOperation itself is dealloc'd? Will this cause a memory leak? Right now if I put a retain on the controller, the crashes goes away. I don't want to leak memory though and need to understand if there are cases where retaining the delegate makes sense. Just to recap. UITableViewController creates an NSOperationQueue and NSOperation that gets embedded into the queue. The UITableViewController passes itself as a delegate to NSOperation. NSOperation calls a method on UITableViewController when it's ready. If I retain the UITableViewController, I guarantee it's there, but I'm not sure if I'm leaking memory. If I only use an assign property, edge cases occur where the UITableViewController gets dealloc'd and objc_msgSend() gets called on an object that doesn't exist in memory and a crash is imminent.

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• Getting JSON object from php authentication objective c

  - by iError

  I am trying to authenticate using the below code NSString *urlAsString =[NSString stringWithFormat:@"http://www.myurl.com/abc/authenticate.php"]; NSURL *url = [NSURL URLWithString:urlAsString]; NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url]; [urlRequest setTimeoutInterval:30.0f]; [urlRequest setHTTPMethod:@"POST"]; [urlRequest addValue:@"test" forHTTPHeaderField:@"m_username" ]; [urlRequest addValue:@"123" forHTTPHeaderField:@"m_password" ]; [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self]; NSOperationQueue *queue = [[NSOperationQueue alloc] init]; [NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response,NSData *data, NSError *error) { if ([data length] >0 && error == nil){ html = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; NSLog(@"HTML = %@", html); receivedData = [NSMutableData data]; } else if ([data length] == 0 && error == nil){ NSLog(@"Nothing was downloaded."); } else if (error != nil){ NSLog(@"Error happened = %@", error); } }]; // Start loading data NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self]; if (theConnection) { // Create the NSMutableData to hold the received data receivedData = [NSMutableData data]; } else { // Inform the user the connection failed. } My username password is correct, I think I am not making the proper call thats why I dont get the desired results and the web service is receiving the null parameters. What can be the issue? Any help appreciated.

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• As-You-Type-Searching with Core Data / NSFetchedResultsController

  - by Snej

  I implemented an as-you-type-searching (text search on single attribute) by fetching with performFetch: after each given character by the user. The performFetch: is running in a background thread to avoid keyboard freezes. But while typing many useless fetches are started. A NSOperationQueue might be an option, but I wonder if there are other approaches for this quite usual search behavior. What's best practice to notice when fetching is done and the table view is updated with the previous fetch to start a new fetch?

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• Objective-C retain counts in dealloc

  - by Michael Waterfall

  I'm seeing something fairly strange here, I've got breakpoints set in various dealloc methods in my app, and on inspection, the retain counts of the object self varies from 1 to 0. When dealloc is called, will the retain count of the object be set to 0 already? I'm using print (int) [self retainCount] in the console to test this. The 0's seem to only appear in the dealloc of my NSOperation's that are being run in an NSOperationQueue. Any idea why this is?

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