尝试获取实体属性的值时出错

Question

我正在尝试从实体属性中获取值：

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.mapaView setDelegate:self];


    MKLocalSearchRequest *request = [[MKLocalSearchRequest alloc] init];
    request.naturalLanguageQuery = self.loja.endereco; // <-- Here
    request.region = self.mapaView.region;

    MKLocalSearch *search = [[MKLocalSearch alloc] initWithRequest:request];

    [search startWithCompletionHandler:^(MKLocalSearchResponse *response, NSError *error)
    {
        NSMutableArray *placemarks = [NSMutableArray array];
        for (MKMapItem *item in response.mapItems) {
            [placemarks addObject:item.placemark];
        }
        [self.mapaView removeAnnotations:[self.mapaView annotations]];
        [self.mapaView showAnnotations:placemarks animated:NO];
    }];
}

但我收到此错误：

2015-08-03 21:01:41.196 MinhaBrasilia[2465:69970] -[__NSCFDictionary endereco]: unrecognized selector sent to instance 0x7fb2faed1910
2015-08-03 21:01:41.199 MinhaBrasilia[2465:69970] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary endereco]: unrecognized selector sent to instance 0x7fb2faed1910'

Loja (self.loja) 是一个实体，它是从 plist 创建的，使用 NSPredicate 过滤，通过方法 tableView:cellForRowAtIndexPath 加载并通过 prepareForSegue:sender 作为参数传递，所有这些都在上一个屏幕中。

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
     LojaTableViewCell *celula = [tableView dequeueReusableCellWithIdentifier:IdentificadorCelula
                                                                forIndexPath:indexPath];

     self.listaFiltrada = [self carregarPlistDeLojasComId:identificadorBtn filtradaPor:self.txtCategoria];

     self.loja = [NSEntityDescription insertNewObjectForEntityForName:@"Loja" inManagedObjectContext:self.managedObjectContext];

     [self.loja setValue:[[self.listaFiltrada objectAtIndex:indexPath.row] objectForKey:@"titulo"] forKey:@"titulo"];
     [self.loja setValue:[[self.listaFiltrada objectAtIndex:indexPath.row] objectForKey:@"subtitulo"] forKey:@"subtitulo"];
     [self.loja setValue:nil forKey:@"categoria"]; //Not implemented
     [self.loja setValue:[[self.listaFiltrada objectAtIndex:indexPath.row] objectForKey:@"endereco"] forKey:@"endereco"];
     [self.loja setValue:nil forKey:@"quadra"]; //Not implemented
     [self.loja setValue:[[self.listaFiltrada objectAtIndex:indexPath.row]  objectForKey:@"telefone"] forKey:@"telefone"];


     [celula preencherCelulaComTitulo:self.loja.titulo
                         comSubtitulo:self.loja.subtitulo
                         comCategoria:self.loja.categoria
                          comEndereco:self.loja.endereco
                            comQuadra:self.loja.quadra
                          comTelefone:self.loja.telefone];

    [celula setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
     return celula;
 }

- (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    self.loja = [self.listaFiltrada objectAtIndex:indexPath.row];
    [self performSegueWithIdentifier:SegueLoja sender:self.loja];
}

#pragma mark - Segue
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if([segue.identifier isEqualToString:SegueLoja]) {
        DetalheViewController *detalheVC = (DetalheViewController *)[[segue destinationViewController] topViewController];
        [detalheVC setLoja:sender];
    }
}

显然我得到了一本字典，如果我这样做request.naturalLanguageQuery = [self.loja valueForKey:@"endereco"];，我可以获得我想要的属性，但这样我相信我没有使用CoreData的资源。

Answer 1

你得到的错误是因为self.loja 是一个字典：在didSelectRowAtIndexPath 你有：

self.loja = [self.listaFiltrada objectAtIndex:indexPath.row];

这是从您过滤的 plist 派生的 NSDictionary，而不是您在 cellForRowAtIndexPath 中创建的 NSManagedObject。字典没有实现endereco 方法，因此出现错误。它确实实现了valueForKey，所以它会起作用：但如果你遵循这条路线，你访问的是字典的键，而不是 NSManagedObject。

我认为您应该重新考虑您的方法 - 使用 cellForRowAtIndexPath 将 plist 处理为 NSManagedObjects 是一个坏主意。它只会为可见单元格调用，并且可能会为同一行调用多次（如果它在屏幕上和屏幕外滚动）。我会编写一个例程将所有 plist 处理为 Core Data，并生成一个 NSManagedObjects 数组，然后您可以将其用作表格视图的数据源。