[NSCFArray length]：发送到实例的无法识别的选择器

Question

I'm trying to fill a table view with some data from an array . The array is populated but when i run the app i get this error : reason: '-[__NSCFArray length]: unrecognized selector sent to instance

I searched for similar questions , but no one was the right for me. I don't use the lenght function and my app is crashing on : cell.textLabel.text = [self.currentDate objectAtIndex:indexPath.row];

quizViewController.m

- (void)passDataForward
{
    ScoreViewController *secondViewController = [[UIStoryboard storyboardWithName:@"Storyboard" bundle:[NSBundle mainBundle]]instantiateViewControllerWithIdentifier:@"score"];

    secondViewController.data =self.scoreLabel.text;
    secondViewController.delegate = self;

    NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
    [highScores insertObject:self.scoreLabel.text atIndex:highScores.count];

    NSData *currentDate =[NSDate date];
    NSDateFormatter *dateFormatter=[[NSDateFormatter alloc]init];
    [dateFormatter setDateFormat:@"dd.MM.YYYY                        HH:mm:ss"];
    NSString *dateString =[dateFormatter stringFromDate:currentDate];

    [data insertObject:dateString atIndex:data.count];



    NSMutableArray *scorearray = [[NSMutableArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] arrayForKey:@"high_scoresarray"]];

     NSMutableArray *dataArray = [[NSMutableArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] arrayForKey:@"data_score"]];

    [scorearray addObject:highScores];
    [dataArray addObject:data];

    [[NSUserDefaults standardUserDefaults] setObject:scorearray forKey:@"high_scoresarray"];
    [[NSUserDefaults standardUserDefaults] setObject:dataArray forKey:@"data_score"];


    secondViewController.test=[NSMutableArray arrayWithArray: scorearray];
    secondViewController.currentDate=[NSMutableArray arrayWithArray: dataArray];

    [self presentViewController:secondViewController animated:YES completion:^(void)
     {

     }];
}

ScoreViewController.m

-(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];
    }
    cell.textLabel.text = [self.currentDate objectAtIndex:indexPath.row];
   cell.detailTextLabel.text=[self.test objectAtIndex:indexPath.row];

    return cell;
}

Answer 1

The error means that this line:

[self.currentDate objectAtIndex:indexPath.row]

returns an Array instead of an NSString. Which means that

self.currentDate

contains NSArray objects and not NSString objects.

Answer 2

Aris is right. self.currentDate returns an NSArray . And that is caused by:

[scorearray addObject:highScores];
[dataArray addObject:data];

Where you are adding one array as the only item to the array scorearray and dataArray respectively. You do not add a bunch of strings, which I assume are stored within highScores and data . Replace it with

[scorearray addObjectsFromArray:highScores];
[dataArray addObjectsFromArray:data];

That should add the contents of highScores and data to scorearray and dataarray .