Question

首先，在我的根视图控制器viewDidLoad中，我使用NSManagedObjects数组初始化一个NSDictionary，如下所示：

- (void)viewDidLoad {
    [super viewDidLoad];
    self.title = @"Decks";

    UIBarButtonItem *browseButton = [[UIBarButtonItem alloc] initWithTitle:@"Browse" style:UIBarButtonItemStylePlain target:self action:@selector(loadBrowseView)];
    self.navigationItem.rightBarButtonItem = browseButton;
    [browseButton release];

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error]) {
    }
    self.categories = [fetchedResultsController fetchedObjects];

    NSMutableDictionary *tipsMutableDictionary = [[NSMutableDictionary alloc] init];
    for (Category *category in self.categories) {
        NSMutableArray *tipsToSort = [NSMutableArray arrayWithArray:[[category valueForKey:@"tips"] allObjects]];

        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending: YES];
        [tipsToSort sortUsingDescriptors: [NSArray arrayWithObject: sortDescriptor]];
        [sortDescriptor release];

        [tipsMutableDictionary setObject:[NSArray arrayWithArray:tipsToSort] forKey:[category name]];
    }
    self.tips = tipsMutableDictionary;
    [tipsMutableDictionary release];
}

现在，“self.tips”（我的根视图控制器上保留的NSDictionary属性）被设置为包含NSManagedObjects的数组。我很高兴地使用该数据大约5分钟（包括将其传递给其他视图的保留属性），直到我收到以下消息：

malloc: *** error for object 0x3b300b0: double free

此时，在错误之后但实际崩溃之前，回溯如下：

#0  0x98152072 in malloc_error_break ()
#1  0x98153218 in szone_error ()
#2  0x9815334d in free_tiny_botch ()
#3  0x01b83064 in _PFDeallocateObject ()
#4  0x01b8d315 in -[_PFManagedObjectReferenceQueue _processReferenceQueue:] ()
#5  0x01bba9ba in _performRunLoopAction ()
#6  0x01d42252 in __CFRunLoopDoObservers ()
#7  0x01d4165f in CFRunLoopRunSpecific ()
#8  0x01d40c48 in CFRunLoopRunInMode ()
#9  0x0252d615 in GSEventRunModal ()
#10 0x0252d6da in GSEventRun ()
#11 0x002a3faf in UIApplicationMain ()
#12 0x00002830 in main (argc=1, argv=0xbfffef60) at /Users/***/main.m:14

值得注意的是，那里没有我的代码。

0x3b300b0上的打印对象显示：

<Tip: 0x3b300b0> (entity: Tip; id: 0x3b2ffe0 <x-coredata://10B4E6EE-ACF3-4316-AE10-6E06E8FFFF46/Tip/p9> ; data: <fault>)

最有趣的是，该地址上的shell malloc_history：

ALLOC 0x3b300b0-0x3b300ef [size=64]: thread_a0a3f500 |start | main | UIApplicationMain | -[UIApplication _run] | CFRunLoopRunInMode | CFRunLoopRunSpecific | PurpleEventCallback | _UIApplicationHandleEvent | -[UIApplication sendEvent:] | -[UIApplication handleEvent:withNewEvent:] | -[UIApplication _reportAppLaunchFinished] | CA::Transaction::commit() | CA::Context::commit_transaction(CA::Transaction*) | CALayerLayoutIfNeeded | -[CALayer layoutSublayers] | -[UILayoutContainerView layoutSubviews] | -[UINavigationController _startDeferredTransitionIfNeeded] | -[UINavigationController _startTransition:fromViewController:toViewController:] | -[UINavigationController _layoutViewController:] | -[UINavigationController _computeAndApplyScrollContentInsetDeltaForViewController:] | -[UIViewController contentScrollView] | -[UIViewController view] | -[RootViewController viewDidLoad] | -[_NSFaultingMutableSet allObjects] | -[_NSFaultingMutableSet willRead] | -[NSManagedObjectContext(_NSInternalAdditions) _retainedObjectWithID:optionalHandler:withInlineStorage:] | +[NSManagedObject(_PFDynamicAccessorsAndPropertySupport) allocWithEntity:] | _PFAllocateObject | malloc_zone_calloc 

----

FREE  0x3b300b0-0x3b300ef [size=64]: thread_a0a3f500 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopDoObservers | _performRunLoopAction | -[_PFManagedObjectReferenceQueue _processReferenceQueue:] | -[NSManagedObjectContext(_NSInternalAdditions) _forgetObject:propagateToObjectStore:] | -[NSManagedObjectContext(_NSInternalAdditions) _forgetObject:propagateToObjectStore:removeFromRegistry:] | CFDictionaryRemoveValue | CFRelease | _PFDeallocateObject | malloc_zone_free 



ALLOC 0x3b300b0-0x3b300cf [size=32]: thread_a0a3f500 |start | main | UIApplicationMain | GSEventRun | GSEventRunModal | CFRunLoopRunInMode | CFRunLoopRunSpecific | __CFRunLoopDoObservers | _performRunLoopAction | -[_PFManagedObjectReferenceQueue _processReferenceQueue:] | _PFDeallocateObject | free_tiny_botch | szone_error | start | _NSPrintForDebugger | -[NSManagedObject description] | +[NSString stringWithFormat:] | -[NSPlaceholderString initWithFormat:locale:arguments:] | _CFStringCreateWithFormatAndArgumentsAux | CFStringCreateMutable | _CFRuntimeCreateInstance | malloc_zone_malloc

我对上面的解释是第一个ALLOC语句中的“[RootViewController viewDidLoad]”是我最初用数据填充NSDictionary的提示。然后在下面的FREE语句中，main.m决定释放这些对象，即使它们在我负责发布的保留的NSDictionary中？

编辑每个请求，这是NSZombieEnabled输出：

*** -[CFString retain]: message sent to deallocated instance 0x3b300b0

之后的Backtrace：

#0  0x01d6a3a7 in ___forwarding___ ()
#1  0x01d466c2 in __forwarding_prep_0___ ()
#2  0x01cfd988 in CFRetain ()
#3  0x01cfd495 in CFArrayCreate ()
#4  0x01d406c3 in -[__NSPlaceholderArray initWithObjects:count:] ()
#5  0x01d4f6f8 in -[NSArray initWithArray:copyItems:] ()
#6  0x01d5c408 in +[NSArray arrayWithArray:] ()
#7  0x0000392f in -[RootViewController getRandomTip:] (self=0x3e1db40, _cmd=0x745b, sender=0x3e27d60) at /Users/***/RootViewController.m:32
#8  0x00299405 in -[UIApplication sendAction:to:from:forEvent:] ()
#9  0x002fcb4e in -[UIControl sendAction:to:forEvent:] ()
#10 0x002fed6f in -[UIControl(Internal) _sendActionsForEvents:withEvent:] ()
#11 0x002fdabb in -[UIControl touchesEnded:withEvent:] ()
#12 0x002b2ddf in -[UIWindow _sendTouchesForEvent:] ()
#13 0x0029c7c8 in -[UIApplication sendEvent:] ()
#14 0x002a3061 in _UIApplicationHandleEvent ()
#15 0x0252ed59 in PurpleEventCallback ()
#16 0x01d41b80 in CFRunLoopRunSpecific ()
#17 0x01d40c48 in CFRunLoopRunInMode ()
#18 0x0252d615 in GSEventRunModal ()
#19 0x0252d6da in GSEventRun ()
#20 0x002a3faf in UIApplicationMain ()
#21 0x00002830 in main (argc=1, argv=0xbfffef60) at /Users/***/main.m:14

上面引用的代码行（/Users/***/RootViewController.m:32）是：

NSArray *tipsArray = [NSArray arrayWithArray:[self.tips objectForKey:categoryNameString]];

我从中可以看出，我试图从“self.tips”访问的对象已经被释放（由谁？为什么？）

Answer 1

使用设置为NSZombieEnabled的环境变量YES重新运行您的程序。这将告诉你何时双重释放对象，以及它是什么对象。或者，您可以使用Zombies工具在Instruments中对此进行调试。

Answer 2

self.tips尚未发布; [self.tips objectForKey:categoryNameString]返回的提示有。它返回了一个错误，而不是一个对象。核心数据将在必要时自动故障对象。

在定义NSFetchRequest时尝试将其放入：

[fetchRequest setReturnsObjectsAsFaults:NO];

这是正在发生的事情：http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/Articles/cdFaultingUniquing.html，如果你想了解更多信息。

我拥有的NSManagedObjects是由main.m发布的？

2 个答案: