Question

我遇到了如何通过didSelectRow PickerView传递托管对象数据的问题。

调试输出发送回“由于未捕获的异常导致应用终止'NSInvalidArgumentException'，原因：' - [Cars isEqualToString：]：无法识别的选择器发送到实例”

我能够成功将相同的数据拉入另一个ViewControler中的表视图中。将它传递给UIPickerView有什么不同？

作为第一个计时器，似乎没有很多资源涉及拣货员和核心数据。任何帮助将不胜感激。

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    // New Grab Data From CoreData Store and populate PlateNumbers Array
    AppDelegate *appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
    _managedObjectContext = [appDelegate managedObjectContext];

    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *cars = [NSEntityDescription entityForName:@"Cars" inManagedObjectContext:_managedObjectContext];
    [request setEntity:cars];

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"created" ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
    [request setSortDescriptors:sortDescriptors];

    NSError *error = nil;
    NSMutableArray *mutableFetchResults = [[_managedObjectContext executeFetchRequest:request error:&error] mutableCopy];

    if (mutableFetchResults == nil) {
    // Handled Error
    }

    [self setPickerPlateNumbers:mutableFetchResults];
    NSLog(@"There are a %u in the car array", [self.pickerPlateNumbers count]);

    [self.ParkZonePicker reloadAllComponents];
}



- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
     return [self.pickerPlateNumbers count];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
        return [self.pickerPlateNumbers objectAtIndex:row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
    NSString *resultString = [[NSString alloc] initWithFormat: @"Car: %@", [self.pickerPlateNumbers objectAtIndex:row]];
    parkCarLabel.text = resultString;
}

**更新**

通过从pickerPlateNumbers数组中寻找的coredata实体传递属性来解决它。

request.resultType = NSDictionaryResultType; request.propertiesToFetch = [NSArray arrayWithObject：[[cars attributesByName] objectForKey：@“numbers”]];

将获取的managedObjectsContext传递给UIPickerView didSelectRow？

0 个答案: