Segue - index 0 beyond bounds for empty array

问题:

Good afternoon,

I'm in the last step of having a TableViewController working and I'm having problems with the DetailViewController.

Here you find my Segue code: I have problems when declaring the "[self.carMakes objectAtIndex:[myIndexPath row]]" because I recieve the error: "[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'" and I have search the error and it's realated my array, that is empty.

I'm going to post below more code if that helps you to find where I'm doing things wrong because I don't know why the array it's empty, because it's showing everything fine in the TableVlewController.

CarTablewViewController.m

@implementation CarTableViewController

@synthesize carMakes = _carMakes;
@synthesize carModels = _carModels;
@synthesize carImages = _carImages;
//@synthesize jsonArray = _jsonArray;

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self fetchJson];

    [self.tableView reloadData];

}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [_jsonArray count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"carTableCell";

    CarTableViewCell *cell = [tableView
                              dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[CarTableViewCell alloc]
                initWithStyle:UITableViewCellStyleDefault
                reuseIdentifier:CellIdentifier];
    }

    cell.makeLabel.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"id"];

    cell.modelLabel.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"user"];

    NSURL * imageURL = [NSURL URLWithString:[[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"imagen"]];
    NSData * imageData = [NSData dataWithContentsOfURL:imageURL];
    UIImage * carPhoto = [UIImage imageWithData:imageData];

    cell.carImage.image = carPhoto;

    return cell;
}

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"ShowCarDetails"])
    {
        CarDetailViewController *detailViewController = [segue destinationViewController];

        NSIndexPath *myIndexPath = [self.tableView indexPathForSelectedRow];

        NSLog(@"TEST");

        detailViewController.carDetailModel = [[NSMutableArray alloc]
                                               initWithObjects:

                                               [self.carMakes objectAtIndex:[myIndexPath row]],
                                               [self.carModels objectAtIndex:[myIndexPath row]],
                                               [self.carImages objectAtIndex:[myIndexPath row]],

                                               nil];
    }
}

-(void)fetchJson {
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{

        NSString * urlString = [NSString stringWithFormat:@"http://website.com/service.php"];
        NSURL * url = [NSURL URLWithString:urlString];
        NSData * data = [NSData dataWithContentsOfURL:url];

        self.carModels = [[NSMutableArray alloc] init];
        self.carMakes = [[NSMutableArray alloc] init];
        self.carImages = [[NSMutableArray alloc] init];
        @try
        {
            NSError *error;
            [_jsonArray removeAllObjects];
            _jsonArray = [NSJSONSerialization
                         JSONObjectWithData:data
                         options:NSJSONReadingMutableContainers|NSJSONReadingMutableLeaves
                         error:&error];
        }
        @catch (NSException * e)
        {
            NSLog(@"Exception: %@", e);
        }
        @finally
        {
            [self.tableView reloadData];
        }
    }
                   );
}

@end

Thanks in advance.

回答1:

Your tableview is using [_jsonArray objectAtIndex:indexPath.row] to populate values. In -(void)fetchJson you are initialising the arrays but not loading them with any data

So when you do this [self.carMakes objectAtIndex:[myIndexPath row]] that array doesn't contain anything

Your table view is using this code to get make and model...

cell.makeLabel.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"id"];

cell.modelLabel.text = [[_jsonArray objectAtIndex:indexPath.row] valueForKey:@"user"];

But your Segue is doing this

[self.carMakes objectAtIndex:[myIndexPath row]],
[self.carModels objectAtIndex:[myIndexPath row]],

In your fetch you are not populating self.carMakes or self.carModels. Either populate them or use

[[_jsonArray objectAtIndex:[myIndexPath row]] valueForKey:@"id"],
[[_jsonArray objectAtIndex:[myIndexPath row]] valueForKey:@"user"],

In your Segue