Question

stRs232Timer* pEvent;
pEvent = (stRs232Timer*)[m_cAppIdMap objectForKey:[NSNumber numberWithUnsignedShort:wTimerIds]];

我收到EXC_BAD_ACCESS错误。为什么会这样？

编辑：

-(BOOL)createTimer
{
    stRs232Timer*   pEvent = malloc(sizeof(stRs232Timer));

    pEvent->bPersistent = YES;                              // setup timer structure
    //pEvent->pStack      = pStack;
    pEvent->wAppTimerId = 95;
    pEvent->uPeriod     = 50;
    pEvent->bStopped    = NO;
    pEvent->uExpirationTime = 10;

    NSLog(@"bPersistent:%d",pEvent->bPersistent);
    NSLog(@"wAppTimerId:%d",pEvent->wAppTimerId);
    NSLog(@"uPeriod:%d",pEvent->uPeriod);
    NSLog(@"bStopped:%d",pEvent->bStopped);


    NSData* myData = [NSData dataWithBytes:(void*)pEvent length:sizeof(stRs232Timer*)];

    wTimerId = 99;
    pEvent->uPeriod = 51;
    myData = [NSData dataWithBytes:(void*)pEvent length:sizeof(stRs232Timer*)];
    [m_cAppIdMap setObject:myData forKey:[NSNumber numberWithUnsignedShort:wTimerId]];
    wTimerId = 96;
    pEvent->uPeriod = 52;
    myData = [NSData dataWithBytes:(void*)pEvent length:sizeof(stRs232Timer*)];
    [m_cAppIdMap setObject:myData forKey:[NSNumber numberWithUnsignedShort:wTimerId]];
    wTimerId = 97;
    pEvent->uPeriod = 53;
    myData = [NSData dataWithBytes:(void*)pEvent length:sizeof(stRs232Timer*)];
    [m_cAppIdMap setObject:myData forKey:[NSNumber numberWithUnsignedShort:wTimerId]];
    wTimerId = 98;
    pEvent->uPeriod = 54;
    myData = [NSData dataWithBytes:(void*)pEvent length:sizeof(stRs232Timer*)];
    [m_cAppIdMap setObject:myData forKey:[NSNumber numberWithUnsignedShort:wTimerId]];
    wTimerId = 95;
    pEvent->uPeriod = 55;
    myData = [NSData dataWithBytes:(void*)pEvent length:sizeof(stRs232Timer*)];
    [m_cAppIdMap setObject:myData forKey:[NSNumber numberWithUnsignedShort:wTimerId]];

    NSLog(@"The dictionary count now is:%d",[m_cAppIdMap count]);
    NSLog(@"The dictionary values now is:");
    NSLog(@"%@",m_cAppIdMap);


    [m_cPendingEventList addObject:myData];
    NSLog(@"EventList:%@",m_cPendingEventList);

    [self StopTimer:99];

return YES;
}

-(BOOL)StopTimer:(unsigned short)wTimerIds
{
    NSLog(@"Into the StopTimer!!");
    stRs232Timer* pEvent;
    BOOL bReturn = NO;
    pEvent = (stRs232Timer*)[m_cAppIdMap objectForKey:[NSNumber numberWithUnsignedShort:wTimerIds]];

    if ([theLock tryLock]) {
        int cnts = [m_cAppIdMap count];
        NSLog(@"The count is:%d",cnts);
           if(pEvent!=nil)
            {
                pEvent->bStopped = YES;
                [m_cAppIdMap removeObjectForKey:[NSNumber numberWithUnsignedShort:wTimerIds]];
                bReturn = YES;
            }
    }
    NSLog(@"My Dictionary value now is:%@",m_cAppIdMap);
    [theLock unlock];
    return bReturn;
}

我调试了代码以查看它导致此异常的位置。[m_cAppIdMap removeObjectForKey：[NSNumber numberWithUnsignedShort：wTimerIds]]; 在stopTimer里面。它出来了。

stRs232Timer是一个指向结构的指针，该结构使用NSData作为NSObject存储在NSDictionary上。

Answer 1

你确定那个代码崩溃了吗？如果wTimerIds是无符号短，则如果密钥不存在，则字典将返回nil。即使没有定义字典，向nil对象发送消息也是有效的，因此不会导致崩溃。

因此，我认为：这次事故发生在其他地方 2. wTimerIds不是无符号的短

Answer 2

m_cAppIdMap可能过早被释放。您可以运行Profiler（使用Zombies工具），如果是这种情况，您将收到一条错误消息，说明在尝试调用objectForKey时已将消息发送到已释放的对象

从字典中获取价值

2 个答案: