以未捕获的NSException类型异常结束-删除表视图行

Question

我正在使用Swift开发一个基于表视图的应用程序。我一整天都在尝试删除tableview行，但我一直得到这个异常。不知道这是什么。这里的代码我必须删除行。不知道还能做些什么来诚实。这应该是一个简单的任务，Swift应该让我们更容易，但这真的是我的阻碍。

代码:

override func tableView(tableView: UITableView!, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath!) {
    let appDel:AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    let context: NSManagedObjectContext = appDel.managedObjectContext
    if editingStyle == UITableViewCellEditingStyle.Delete {
            // do something with unwrappedIndexPath.row
            context.deleteObject(myData.objectAtIndex(indexPath.row) as NSManagedObject)
            tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic)
        var error: NSError? = nil
        if !context.save(&error) {
            abort()
        }
    }
}

埃罗:

(
    "<MyData: 0x10bba1a90> (entity: MyData; id: 0xd0000000001c0000 <x-coredata://8A0231EE-899F-48F9-953B-CAB1252FD1D0/MyData/p7> ; data: <fault>)"
)
<MyData: 0x10d84ba20> (entity: MyData; id: 0xd000000000300000 <x-coredata://8A0231EE-899F-48F9-953B-CAB1252FD1D0/MyData/p12> ; data: {
    name = test;
    skills = te;
})
Data Saved
(
    "<MyData: 0x10bba1a90> (entity: MyData; id: 0xd0000000001c0000 <x-coredata://8A0231EE-899F-48F9-953B-CAB1252FD1D0/MyData/p7> ; data: {n    name = Rob;n    skills = Dev;n})",
    "<MyData: 0x10bf1dec0> (entity: MyData; id: 0xd000000000300000 <x-coredata://8A0231EE-899F-48F9-953B-CAB1252FD1D0/MyData/p12> ; data: <fault>)"
)
2014-06-13 21:51:51.452 coreDataApp[2090:38878] *** Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-3185.20/UITableView.m:1487
2014-06-13 21:51:51.487 coreDataApp[2090:38878] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 0.  The number of rows contained in an existing section after the update (2) must be equal to the number of rows contained in that section before the update (2), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000100848e35 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x00000001022f49a0 objc_exception_throw + 45
    2   CoreFoundation                      0x0000000100848c9a +[NSException raise:format:arguments:] + 106
    3   Foundation                          0x0000000100cdb6fb -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 195
    4   UIKit                               0x0000000101190b3b -[UITableView _endCellAnimationsWithContext:] + 11785
    5   coreDataApp                         0x000000010000454c _TFC11coreDataApp23dataTableViewController9tableViewfS0_FTGSQCSo11UITableView_18commitEditingStyleOSC27UITableViewCellEditingStyle17forRowAtIndexPathGSQCSo11NSIndexPath__T_ + 2332
    6   coreDataApp                         0x0000000100004927 _TToFC11coreDataApp23dataTableViewController9tableViewfS0_FTGSQCSo11UITableView_18commitEditingStyleOSC27UITableViewCellEditingStyle17forRowAtIndexPathGSQCSo11NSIndexPath__T_ + 103
    7   UIKit                               0x00000001011b1e51 -[UITableView animateDeletionOfRowWithCell:] + 114
    8   UIKit                               0x00000001013409db -[UITableViewCell _swipeDeleteButtonPushed] + 60
    9   UIKit                               0x00000001010c4333 -[UIApplication sendAction:to:from:forEvent:] + 75
    10  UIKit                               0x00000001011c086d -[UIControl _sendActionsForEvents:withEvent:] + 467
    11  UIKit                               0x00000001011bfc3f -[UIControl touchesEnded:withEvent:] + 522
    12  UIKit                               0x000000010144efb7 _UIGestureRecognizerUpdate + 7670
    13  UIKit                               0x0000000101105d66 -[UIWindow _sendGesturesForEvent:] + 1041
    14  UIKit                               0x0000000101106993 -[UIWindow sendEvent:] + 667
    15  UIKit                               0x00000001010d7dd1 -[UIApplication sendEvent:] + 246
    16  UIKit                               0x00000001010e2dda _UIApplicationHandleEventFromQueueEvent + 11315
    17  UIKit                               0x00000001010bfc5f _UIApplicationHandleEventQueue + 1461
    18  CoreFoundation                      0x000000010077fbd1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    19  CoreFoundation                      0x000000010077522d __CFRunLoopDoSources0 + 269
    20  CoreFoundation                      0x000000010077485d __CFRunLoopRun + 861
    21  CoreFoundation                      0x0000000100774296 CFRunLoopRunSpecific + 470
    22  GraphicsServices                    0x0000000104462ce4 GSEventRunModal + 161
    23  UIKit                               0x00000001010c3308 UIApplicationMain + 2994
    24  coreDataApp                         0x00000001000096ad top_level_code + 77
    25  coreDataApp                         0x00000001000096ea main + 42
    26  libdyld.dylib                       0x0000000102852145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

Answer 1

忘记从数据模型中删除对象

myData.removeObjectAtIndex(indexPath!.row)

这不是Swift的问题，在Obj-C中也会发生。

Answer 2

通过在展开前测试两个可选选项(tableView和indexPath)来实现更安全的方法:

func tableView(tableView: UITableView?, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath?) {
    let appDel:AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
    let context: NSManagedObjectContext = appDel.managedObjectContext
    if editingStyle == UITableViewCellEditingStyle.Delete {
        // do something with unwrappedIndexPath.row
        if let ind = indexPath? {
            context.deleteObject(myData.objectAtIndex(ind.row) as NSManagedObject)
            tableView?.deleteRowsAtIndexPaths([ind], withRowAnimation: .Automatic)
        }
        var error: NSError? = nil
        if !context.save(&error) {
            abort()
        }
    }
}

Answer 3

在tableView数据操作中，顺序很重要。首先从数据模型中删除对象，然后删除行。

myData.removeObjectAtIndex(indexPath!.row)
tableView?.deleteRowsAtIndexPaths([ind], withRowAnimation: .Automatic)

这个线程有点旧了，但是为了帮助其他人从搜索中得到帮助，在swift 4中，这看起来像这样:

myData.remove(indexPath.row)
tableView?.deleteRows(at: [indexPaths], with: .Automatic)