IOS 5 消息通过 alloc 命令发送到已解除分配的实例

Question

我在使用 ARC 的 Ios 5 应用程序上出现以下错误：

    *** -[ViewDettaglio respondsToSelector:]: message sent to deallocated instance 0x12193300

在控制台上编写命令：

    info malloc-history 0x12193300

并且得到以下堆栈跟踪：

    Alloc: Block address: 0x12193300 length: 192
    Stack - pthread: 0xa08a3540 number of frames: 31
        0: 0x96bdab03 in malloc_zone_calloc
        1: 0x96bdaa5a in calloc
        2: 0x16f8c93 in class_createInstance
        3: 0x170388b in _objc_rootAllocWithZone
        4: 0x21af661 in +[NSObject allocWithZone:]
        5: 0x17038b9 in _objc_rootAlloc
        6: 0x2c4c8 in -[ViewElenco CaricaViewDettaglio:] at /Users/.../ViewElenco.m:186
        7: 0x2e550 in -[ViewElenco mapView:annotationView:calloutAccessoryControlTapped:] at /Users/.../ViewElenco.m:337
        8: 0x3fa99c
        9: 0x405faa in MKLongHash
       10: 0x21aeec9 in -[NSObject performSelector:withObject:withObject:]
       11: 0x60d5c2 in -[UIApplication sendAction:to:from:forEvent:]
       12: 0x60d55a in -[UIApplication sendAction:toTarget:fromSender:forEvent:]
       13: 0x6b2b76 in -[UIControl sendAction:to:forEvent:]
       14: 0x6b303f in -[UIControl(Internal) _sendActionsForEvents:withEvent:]
       15: 0x6b22fe in -[UIControl touchesEnded:withEvent:]
       16: 0x632a30 in -[UIWindow _sendTouchesForEvent:]
       17: 0x632c56 in -[UIWindow sendEvent:]
       18: 0x619384 in -[UIApplication sendEvent:]
       19: 0x60caa9 in _UIApplicationHandleEvent
       20: 0x1a95fa9 in PurpleEventCallback
       21: 0x21811c5 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__
       22: 0x20e6022 in __CFRunLoopDoSource1
       23: 0x20e490a in __CFRunLoopRun
       24: 0x20e3db4 in CFRunLoopRunSpecific
       25: 0x20e3ccb in CFRunLoopRunInMode
       26: 0x1a94879 in GSEventRunModal
       27: 0x1a9493e in GSEventRun
       28: 0x60aa9b in UIApplicationMain
       29: 0x20bb in main at /Users/.../main.m:14
       30: 0x2065 in start

ViewElenco.m 第 186 行的代码如下：

    ViewDettaglio *viewq=[[ViewDettaglio alloc] initWithNibName:@"ViewDettaglio" bundle:nil];

这是怎么发生的？ 我正在使用 UINavigationController 从 ViewElenco 和 ViewDettaglio 进行导航。

编辑

以下代码中是否有可能：

    ViewDettaglio* viewDettaglio=[[ViewDettaglio alloc] initWithNibName:@"ViewDettaglio" bundle:nil];
    viewDettaglio.idObject=idObj;
    [self.navigationController pushViewController:viewDettaglio animated:YES];

alloc返回一个已释放的对象？

Answer 1

问题已经解决：在ViewDettaglio和ViewElenco中有一个MKMapView，并且委托被设置为容器ViewController。
当在 UINavigationController 中推送新的 ViewController 时，MapView 创建的某些线程可能仍在运行并调用地图委托，即使它不可见。

解决方案是在视图消失时将 delegate 设置为 null，并在视图出现之前再次设置：

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    self.mapView.delegate=nil;
}
- (void)viewWillAppear:(BOOL)animated
{    
    [super viewWillAppear:animated];
    self.mapView.delegate=self;
}