MagicalRecord 中的 findFirstByAttribute 再次找到已删除的实体

Question

我正在使用 MagicalRecord 和 CoreData Wrapper 在我的应用程序中实现最喜欢的场景。我正在搜索如果在我的实体中找到该属性的值，它会将其作为 fav 删除，否则会将其添加到 fav。在此处执行DX *foundDX = [DX MR_findFirstByAttribute:@"code" withValue:cell.DXCodeName.text]; foundDX 是我正在检查的值。
我已将 UISearchBar 添加到我的 tableView 中。因此，当视图被加载时，它会显示已经收藏的项目，这些项目使用可以取消收藏。如果用户搜索并选择一个项目，它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 和foundDX 第一次没有找到并添加到数据模型中。然后再次按下 fav 按钮将其删除，实际上它确实删除了它。但是，如果我再次点击 fav 按钮，foundDX 仍然是E45，因此它崩溃了。但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 我正在这样做：

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

现在它在前两次工作正常意味着添加/删除/添加/删除。之后它只运行 if (!foundDX.code) 块，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。应该是这样的：

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/删除使您处于您期望的状态，即您拥有已添加或删除的内容