Backendless：删除第一个 table 中的行，当另一个 table 中的相关行被删除时

Question

我有两个 table。用户收藏夹和操作。 UserFavourites 将 Action 作为其属性（列）。当在 Action table 中删除相关 Action 时，我希望系统删除 UserFavourite 行。目前，当我在 Action table 中删除一行，即 UserFavourites 的 child 时，UserFavourites 的 Action 列为空列，但它并没有像我希望的那样被删除。非常感谢！

编辑： 我想我应该加载相关的 UserFavourites object 并像这样删除它：

  ActionCreation* uf = [self.myActions objectAtIndex:self.selectedIndex.row];
    BackendlessDataQuery *query = [BackendlessDataQuery query];
            Fault *fault=nil;
            query.whereClause = [NSString stringWithFormat:@"favouriteAction.objectId =\'%@\'", [uf objectId]];
    @try{
                BackendlessCollection* relatedUserFavourites =[backendless.persistenceService load:uf relations:@[@"*"]error:&fault];

//code for delteing from backendless
            }@catch (Fault *fault) {

                NSLog(@"FAULT = %@ <%@>", fault.message, fault.detail);

            }

但我得到异常：

-[ActionCreation allKeys]: unrecognized selector sent to instance 0x7fa8b0fc59c0
2015-03-11 19:57:03.157 ActionPlusChetech[1468:76482] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[ActionCreation allKeys]: unrecognized selector sent to instance 0x7fa8b0fc59c0'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010c476a75 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010c10fbb7 objc_exception_throw + 45
    2   CoreFoundation                      0x000000010c47dd1d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x000000010c3d59dc ___forwarding___ + 988
    4   CoreFoundation                      0x000000010c3d5578 _CF_forwarding_prep_0 + 120
    5   ActionPlusChetech                   0x00000001098322a2 -[PersistenceService load:relations:] + 331
    6   ActionPlusChetech                   0x0000000109830ed7 -[PersistenceService load:relations:error:] + 30
    7   ActionPlusChetech                   0x00000001097f4bb7 -[MyActionsVC deleteButtonTapped] + 1767
    8   ActionPlusChetech                   0x00000001097f66be -[MyActionsVC pushMenuItem:] + 526
    9   Foundation                          0x000000010a611e3a -[NSObject(NSThreadPerformAdditions) performSelector:onThread:withObject:waitUntilDone:modes:] + 900
    10  Foundation                          0x000000010a611971 -[NSObject(NSThreadPerformAdditions) performSelectorOnMainThread:withObject:waitUntilDone:] + 132
    11  ActionPlusChetech                   0x00000001097f750d -[KxMenuItem performAction] + 157
    12  ActionPlusChetech                   0x00000001097f9940 -[KxMenuView performAction:] + 208
    13  UIKit                               0x000000010abc9a22 -[UIApplication sendAction:to:from:forEvent:] + 75
    14  UIKit                               0x000000010acd0e50 -[UIControl _sendActionsForEvents:withEvent:] + 467
    15  UIKit                               0x000000010acd021f -[UIControl touchesEnded:withEvent:] + 522
    16  UIKit                               0x000000010af77e80 _UIGestureRecognizerUpdate + 9487
    17  UIKit                               0x000000010ac0f856 -[UIWindow _sendGesturesForEvent:] + 1041
    18  UIKit                               0x000000010ac10483 -[UIWindow sendEvent:] + 667
    19  UIKit                               0x000000010abdcfb1 -[UIApplication sendEvent:] + 246
    20  UIKit                               0x000000010abea227 _UIApplicationHandleEventFromQueueEvent + 17700
    21  UIKit                               0x000000010abc523c _UIApplicationHandleEventQueue + 2066
    22  CoreFoundation                      0x000000010c3abc91 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    23  CoreFoundation                      0x000000010c3a1b5d __CFRunLoopDoSources0 + 269
    24  CoreFoundation                      0x000000010c3a1194 __CFRunLoopRun + 868
    25  CoreFoundation                      0x000000010c3a0bc6 CFRunLoopRunSpecific + 470
    26  GraphicsServices                    0x000000010ef49a58 GSEventRunModal + 161
    27  UIKit                               0x000000010abc8580 UIApplicationMain + 1282
    28  ActionPlusChetech                   0x00000001097ea9e3 main + 115
    29  libdyld.dylib                       0x000000010d106145 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

我不太明白这个错误。 -[ActionCreation allKeys]:和taht有什么关系？并且没有捕获到 Backendless 异常。谢谢。

Answer 1

好吧，我找到了解决方法。不完全是我想要的，但它有效。因为 UserFavourites 在删除相关操作 object 后有空列，我的应用程序抛出异常，因为它获取的值为空。所以我决定，每次用户加载他的收藏夹时，检查 Action 列是否为空，如果是 - 他们发送请求删除 UserFavourites object。遗憾的是，我无法想出一种方法使这两列像 SQL 一样相互依赖，例如更新时、删除时等等。但是，嘿，它有效！）希望这对遇到此问题的人有所帮助。

Backendless：删除第一个 table 中的行，当另一个 table 中的相关行被删除时

Backendless: delete row in 1st table when related row in another table is deleted

ios

backendless