Question

我有一个包含单个实体对象的核心数据模型。然后我将这些对象加载到一个数组中，并将它们显示在具有默认单元格样式的表中。在导航栏中有一个删除按钮，当选择一行（例如对象）并单击此按钮时，它应该删除核心模型中的行和相应的对象。我见过删除行的示例，但每行显示一个删除按钮。我想在导航栏中只有一个按钮，并能够控制从中删除行。我已经尝试过下面的代码，但它不起作用。我无法找到一种方法来识别delete方法中选择的行。任何帮助表示赞赏。

在tableviewcontroller类的viewdidload中：

 UIBarButtonItem *delButton = [[UIBarButtonItem alloc]
                                  initWithTitle:@"Del"
                                  style: UIBarButtonItemStyleBordered
                                  target: self
                                  action:@selector(delItemToArray)];


self.managedObjectContext = ((ecoAppDelegate *) [UIApplication sharedApplication].delegate).managedObjectContext;



NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
                               entityForName:@"FavoritesInfo" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];

fetchRequest.resultType = NSDictionaryResultType;

[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"name", nil]];



  NSError *error=nil;

self.favArr=[self.managedObjectContext executeFetchRequest:fetchRequest error:&error];


if (error!=nil) {
    NSLog(@" fetchError=%@,details=%@",error,error.userInfo); 
}


self.favName = [self.favArr valueForKey:@"name"];




//Delete Item To table array and delete object to data core model

    - (void)delItemToArray {

        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];

        NSManagedObjectContext *context = [appDelegate managedObjectContext];

        [context deleteObject:appDelegatee.favoritesInfo]; // favoritesInfo is the NSManagedObject

        NSIndexPath *indexPath;
        [favName removeObjectAtIndex:indexPath.row];

        [appDelegatee saveContext]; // to save changes in the core data model

        [self.tableView reloadData];
    }

错误：

  [__NSArrayI removeObjectAtIndex:]: unrecognized selector sent to instance 0x8852b90
    *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayI removeObjectAtIndex:]: unrecognized selector sent to instance 0x8852b90'

Answer 1

您可能会收到Incompatible pointer types initializing 'NSMutableArray *' with an expression of type 'NSArray *'这里的警告

self.favArr=[self.managedObjectContext executeFetchRequest:fetchRequest error:&error];

您应该使fetched数组可变，以便从中删除对象。你可以像

那样做

self.favArr  = [[self.managedObjectContext executeFetchRequest:fetchRequest error:&error] mutableCopy];

同时更改此

self.favName = [self.favArr valueForKey:@"name"];

到

self.favName = [[self.favArr valueForKey:@"name"]mutableCopy];

使用一个按钮从核心数据中删除表格行和同时对象

1 个答案: