被删除的实体再次被findFirstByAttribute在MagicalRecord中找到

问题描述：

我正在实现使用MagicalRecord和CoreData Wrapper的应用程序中的收藏场景。我正在寻找的价值，如果在我的实体中找到该属性，它会删除它作为最喜欢的，否则它会将它添加到最喜欢的。在这里做DX *foundDX = [DX MR_findFirstByAttribute:@"code" withValue:cell.DXCodeName.text]; foundDX是我正在检查的值。
我有一个UISearchBar添加到我的tableView。所以当视图被加载的时候，它会显示已经使用过的最不喜欢的项目。如果用户搜索并选择一个项目，它会成功将它添加到fav并成功从数据模型中删除它。但如果我再次点击收藏按钮，它会崩溃。被删除的实体再次被findFirstByAttribute在MagicalRecord中找到

if (!foundDX.code) { 
     //If we are always getting into here that means that either foundDX is nil 
     //or the code is nil so you need to verify the logic around that. 
     if (indexPath != nil) 
     { 
      if (!_AddEditDX) { 
       self.AddEditDX = [DX MR_createEntity]; 
      } 
      [self.AddEditDX setCode:cell.DXCodeName.text]; 
      [self.AddEditDX setDescriptions:cell.DXDescText.text]; 
      [self.AddEditDX setIsFav:[NSNumber numberWithInt:1]]; 

      [[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait]; 
      [self.favDXArray addObject:self.AddEditDX]; 
      [self fetchFavDX]; 

      [cell.DXFavButton setImage:[UIImage imageNamed:@"star_filled"] forState:UIControlStateNormal]; 
      [KSToastView ks_showToast:@"Added to Favourite" duration:1.0f]; 

     } 
    } else if(self.favDXArray.count > indexPath.row) { 
     //You can get rid of the if(foundDX.code) because this is the else block to not having it so we must have it. 
     //Only thing to worry about is the array size 
     NSLog(@"count is: %ld and row is: %ld",_favDXArray.count, (long)indexPath.row); 
     DX *tempDX = [self.favDXArray objectAtIndex:indexPath.row]; 
     [tempDX MR_deleteEntity]; 

     [cell.DXFavButton setImage:[UIImage imageNamed:@"star_blank"] forState:UIControlStateNormal]; 
     [self.favDXArray removeObjectAtIndex:indexPath.row]; 
     [[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait]; 
     [KSToastView ks_showToast:@"Removed from Favourite" duration:1.0f]; 
    }

通过应用一些断点我发现：
假设代码是E45和foundDX没有发现它的第一次，并把它添加到数据模型。然后再次按下fav按钮将其删除，实际上删除它。但如果我再次点击收藏按钮，foundDX仍然E45，因此它崩溃。但是，如果我关闭应用程序并再次运行它，则E45不再存在。

UPDATE
我已更新上面的代码。我在viewDidLoad中使用fetchFavDX，所以我尝试在上面的代码中更新的方法中调用它。而在fetchFavDX我这样做：

-(void)fetchFavDX { 
    self.favDXArray = [NSMutableArray arrayWithArray:[DX MR_findAllSortedBy:@"code" ascending:YES]]; 
}

现在是前两个时代意义添加/删除/添加/删除工作的罚款。之后，它只运行if (!foundDX.code)块，这意味着它没有进入其他部分。

您是否可以使用崩溃日志更新上述内容？请 – HarmVanRisk

@HarmVanRisk它的索引0超出了空数组的边界，这表明对象被删除，如果我再次运行应用程序，这是正确的。但是，如果它是相同的运行它崩溃与此错误。 –

答

您应该检查self.favDXArray计数是否比indexpath.row更长，以便有实际移除/检索的内容。这将是这样的：

if(self.favDXArray.count > indexPath.row){ 
    DX *tempDX = [self.favDXArray objectAtIndex:indexPath.row]; 
    [tempDX MR_deleteEntity]; 
    [cell.DXFavButton setImage:[UIImage imageNamed:@"star_blank"] forState:UIControlStateNormal]; 
    [self.favDXArray removeObjectAtIndex:indexPath.row]; 
    [KSToastView ks_showToast:@"Removed from Favourite" duration:1.0f]; 
    [[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait]; 
}

更新

if (!foundDX.code) { 
//If we are always getting into here that means that either foundDX is nil 
//or the code is nil so you need to verify the logic around that. 
    if (indexPath != nil) 
    { 
     self.AddEditDX = [DX MR_createEntity]; 
     [self.AddEditDX setCode:cell.DXCodeName.text]; 
     [self.AddEditDX setDescriptions:cell.DXDescText.text]; 
     [self.AddEditDX setIsFav:[NSNumber numberWithInt:1]]; 

     [[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait]; 
     [self.favDXArray addObject:self.AddEditDX]; 
     [self fetchFavDX]; 

     [cell.DXFavButton setImage:[UIImage imageNamed:@"star_filled"] forState:UIControlStateNormal]; 
     [KSToastView ks_showToast:@"Added to Favourite" duration:1.0f]; 

    } 
} else if(self.favDXArray.count > indexPath.row) { 
//You can get rid of the if(foundDX.code) because this is the else block to not having it so we must have it. 
//Only thing to worry about is the array size 
    NSLog(@"count is: %ld and row is: %ld",_favDXArray.count, (long)indexPath.row); 
    DX *tempDX = [self.favDXArray objectAtIndex:indexPath.row]; 
    [tempDX MR_deleteEntity]; 

    [cell.DXFavButton setImage:[UIImage imageNamed:@"star_blank"] forState:UIControlStateNormal]; 
    [self.favDXArray removeObjectAtIndex:indexPath.row]; 
    [[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait]; 
    [KSToastView ks_showToast:@"Removed from Favourite" duration:1.0f]; 
}

确保方法来获取foundDX将返回你期待什么。另外，请确保添加/删除功能将您置于所期望的状态，即您拥有添加或删除的内容

这个答案给了我一些东西，我可以感觉到我即将完成它。你能否看到更新的问题并相应地更新你的答案。 –

@TalhaCh我已尽我所能地更新了您所提供的内容。希望它会帮助你 – HarmVanRisk

现在，如果我运行该项目，它第一次运行它意味着添加>删除>添加，那么它似乎'[self.favDXArray addObject：self.AddEditDX];'没有添加值。因为在此之后计数为零。这是因为它正在重复我的想法。 –

被删除的实体再次被findFirstByAttribute在MagicalRecord中找到

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