ios - SearchBar 在第一个字符后崩溃 -Core Data

Question

每当我尝试在 SearchBar 中输入第二个字符时，应用程序就会崩溃并出现“因未捕获的异常而终止”错误。如果有帮助，SearchBar 将引用表格单元格数据。我该如何解决这个问题？

@interface DeviceViewController ()
@property (strong) NSMutableArray *devices;
@end

@implementation DeviceViewController
{
    NSArray *searchResults;
}
- (NSManagedObjectContext *)managedObjectContext {
    NSManagedObjectContext *context = nil;
    id delegate = [[UIApplication sharedApplication] delegate];
    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }
    return context;
}
- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
    //label.backgroundColor = [UIColor clearColor];
    label.font = [UIFont fontWithName:@"HelveticaNeue-thin" size:28];
    //label.shadowColor = [UIColor colorWithWhite:0.0 alpha:0.5];
    label.textColor = [UIColor blackColor];
    self.navigationItem.titleView = label;
    label.text = @"TapNotes";
    [label sizeToFit];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    // Fetch the devices from persistent data store
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Device"];
    self.devices = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];

    [self.tableView reloadData];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (tableView == self.searchDisplayController.searchResultsTableView) {
        return [searchResults count];

    } else {
        return self.devices.count;
    }
    //return self.devices.count;
    }
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell==nil) {
        cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier]; }
    NSManagedObject *device = [self.devices objectAtIndex:indexPath.row];
    [cell.textLabel setText:[NSString stringWithFormat:@"%@", [device valueForKey:@"name"]]];
    [cell.detailTextLabel setText:[NSString stringWithFormat:@"%@",[device valueForKey:@"version"]]];
    if (tableView == self.searchDisplayController.searchResultsTableView) {
        device = [searchResults objectAtIndex:indexPath.row];
    } else {
        [self.devices objectAtIndex:indexPath.row];
    }

   // cell.thumbnailImageView.image = [UIImage imageNamed:recipe.image];

    return cell;
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the specified item to be editable.
    return YES;
}


- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObjectContext *context = [self managedObjectContext];

    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete object from database
        [context deleteObject:[self.devices objectAtIndex:indexPath.row]];

        NSError *error = nil;
        if (![context save:&error]) {
            NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);
            return;
        }

        // Remove device from table view
        [self.devices removeObjectAtIndex:indexPath.row];
        [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }
}

/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}
*/

/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"UpdateDevice"]) {
        NSManagedObject *selectedDevice = [self.devices objectAtIndex:[[self.tableView indexPathForSelectedRow] row]];
         NSIndexPath *indexPath = nil;
        if (self.searchDisplayController.active) {
            indexPath = [self.searchDisplayController.searchResultsTableView indexPathForSelectedRow];
            _devices = [searchResults objectAtIndex:indexPath.row];
        } else {
            indexPath = [self.tableView indexPathForSelectedRow];
            _devices = [_devices objectAtIndex:indexPath.row];
        }
        DeviceDetailViewController *destViewController = segue.destinationViewController;
        destViewController.device = selectedDevice;
    }
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 55;
}
- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope
{
    NSPredicate *resultPredicate = [NSPredicate predicateWithFormat:@"name contains[c] %@", searchText];
    searchResults = [_devices filteredArrayUsingPredicate:resultPredicate];
}
-(BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString
{
    [self filterContentForSearchText:searchString
                               scope:[[self.searchDisplayController.searchBar scopeButtonTitles]
                                      objectAtIndex:[self.searchDisplayController.searchBar
                                                     selectedScopeButtonIndex]]];

    return YES;
}
@end

Answer 1

您有很多 TableView 管理问题。

正如我提到的 HERE , 使用 NSFetchedResultsController (或者打开一个包含 CoreData 的空项目，看看当你有一个表管理时会有多容易)。

您不能在不通知表需要重新加载它的情况下过滤您的搜索数组。
TableView 必须知道数据源的计数，因为当它在 cellForRow...

中请求时，它会期望该数据存在

此外，您将 _device 变量一次视为 NSArray，将一个视为托管对象(在 cellForRow... 中) ).

在 cellForRow... 中将 _device 更改为 device ...
然后你会遇到一个新问题......

(看看我在你之前的问题中给你的建议)