是否由于未捕获的异常“ NSInvalidArgumentException”而终止应用程序？

Question

I cannot figure out why as soon as I try to use the [mainArray addObject:] expression my whole program fails! If i pass it strings it works just fine, but as soon as i try to pass it a variable it fails, any help?

#import "AG_ViewController.h"
#import "AG_Storage.h"
#import "AG_AddItemViewController.h"

@interface AG_ViewController ()



@end

@implementation AG_ViewController

- (void)viewDidLoad {
    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.

    mainArray = [NSMutableArray array];


    AG_Storage *item1 = [[AG_Storage alloc] init];
    item1.itemName = @"Test";

    NSLog(@"Add item1");
    NSLog(@"%@",mainArray);

    AG_Storage *item2 = [[AG_Storage alloc] init];
    item2.itemName = @"Test2";


    NSLog(@"Add item2");
    [mainArray addObject:item1];
    NSLog(@"%@", mainArray);

     }

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
    return [mainArray count]; }


- (UITableViewCell *)tableView:(UITableView *)tableViewer cellForRowAtIndexPath:(NSIndexPath *)indexPath{

    UITableViewCell *cell = [tableViewer dequeueReusableCellWithIdentifier:@"thisCell"];
    cell.textLabel.text = [mainArray objectAtIndex:indexPath.row];
    return cell; }

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

@end

I initialized mainArray in the header file,

@interface AG_ViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>{

IBOutlet UITableView *tableView;

NSMutableArray *mainArray;

}

Log is as follows:

2014-03-18 13:49:26.028 AgendaBk[22575:a0b] Add item1
2014-03-18 13:49:26.030 AgendaBk[22575:a0b] (
)
2014-03-18 13:49:26.030 AgendaBk[22575:a0b] Add item2
2014-03-18 13:49:26.031 AgendaBk[22575:a0b] (
    "<AG_Storage: 0x895bdc0>"
)
2014-03-18 13:49:26.036 AgendaBk[22575:a0b] -[AG_Storage length]: unrecognized selector sent to instance 0x895bdc0
2014-03-18 13:49:26.039 AgendaBk[22575:a0b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[AG_Storage length]: unrecognized selector sent to instance 

Junk here

libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

Note (you probably don't actually have it in your code, but anyway): Don't forget NSMutableArray *mainArray = [NSMutableArray array]

Try to use [mainArray addObjectsFromArray:@[item1, item2]];

Answer 2

Try this way

 - (void)viewDidLoad
    {
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.

       NSMutableArray *mainArray = [NSMutableArray array];

        AG_Storage *item1 = [[AG_Storage alloc] init];
        item1.itemName = @"Test";
        NSLog(@"Add item1");
        NSLog(@"%@",mainArray);

        AG_Storage *item2 = [[AG_Storage alloc] init];
        item2.itemName = @"Test2";
        NSLog(@"Add item2");
        [mainArray addObjectsFromArray:[NSArray arrayWithObjects: item1, item2, nil]];
        NSLog(@"%@",mainArray);


    }

Thanks

Answer 3

I think you don't quite understand the difference between an instance variable and a local variable. If your first code version compiled and you haven't changed your properties, then your first example assigned an NSMutableArray* to an instance variable, where it stays until that view is deallocated, while the second example assigned an NSMutableArray* to a local variable, where ARC will deallocate it as soon as the method returns. item1 and item2 will disappear as well.

It is highly recommended to start instance variables with an underscore (like _mainArray), to make it more obvious what you are doing.

Sorry, just noticed that it was someone else changing the instance variable to a local variable.