ios - Removed Entity 再次被 MagicalRecord 中的 findFirstByAttribute 找到

Question

我正在使用 MagicalRecord 和 CoreData Wrapper 在我的应用程序中使用 Favorite 场景。我正在搜索的值是，如果在我的实体中找到该属性，它会将其作为收藏夹删除，否则会将其添加到收藏夹。在此处执行操作到我的 TableView 。因此，当加载 View 时，它会显示已经收藏的项目，这些项目可以取消收藏。如果用户搜索并选择一个项目，它会成功地将其添加到收藏夹并成功地将其从数据模型中删除。但是，如果我再次点击收藏按钮，它就会崩溃。

   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并且foundDX没有第一次找到它并添加到数据中模型。然后再次按下 fav 按钮将其删除，实际上它确实将其删除。但是，如果我再次点击 fav 按钮，foundDX 仍然是 E45，因此它会崩溃。但是如果我关闭应用程序并再次运行它，E45 将不再存在。

更新
我已经更新了上面的代码。我在 viewDidLoad 中使用了 fetchFavDX，所以我尝试在上面代码中更新的方法中调用它。而在 fetchFavDX 中，我这样做:

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

现在它在前两次工作正常，这意味着添加/删除/添加/删除。之后，它只运行 if (!foundDX.code) block ，这意味着它不会进入 else 部分。

Answer 1

您应该检查 self.favDXArray 计数是否比 indexpath.row 长，以便实际删除/检索某些内容。它会是这样的:

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];
}

确保获取 foundDX 的方法返回您所期望的。还要确保添加/删除让您处于您期望的状态，即您拥有已添加或删除的内容