Why are my mutable arrays and table views behaving unexpectedly?

Question

I'm building a sign-in app. It has two table views. One lists people who have visited before (existingNames), and one lists the current people signed in (names).

At certain points in my code the only mutable array that does not crash the program when accessed is names.

names and existingNames seems to somehow be reversed as well. When I try to remove from names, the program crashes. When I remove from existingNames, the changes are reflected in tableView2, but tableView2 is supposed to be associated with names.

In the app's current state everything is "working" except for accessing any company arrays. I put quotes around working because of the names and existingNames being used backwards.

Any insight into what might be causing the problem would be much appreciated!

.h:

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UITableViewDataSource, UITableViewDelegate>{
    UITableView *tableView;
}

@property (weak, nonatomic) IBOutlet UITextField *nameField;
@property (weak, nonatomic) IBOutlet UITextField *companyField;
@property (nonatomic, retain) NSMutableArray *names;
@property (nonatomic, retain) NSMutableArray *companies;
@property (nonatomic, retain) NSMutableArray *existingNames;
@property (nonatomic, retain) NSMutableArray *existingCompanies;

- (IBAction)add:(id)sender;
- (IBAction)addExisting:(id)sender;
- (IBAction)remove:(id)sender;
- (IBAction)submit:(id)sender;

@property (strong, nonatomic) IBOutlet UITableView *tableView1;
@property (weak, nonatomic) IBOutlet UITableView *tableView2;

@end

.m:

#import "ViewController.h"
#import <MessageUI/MessageUI.h>

@interface ViewController () <MFMailComposeViewControllerDelegate>

@end

@implementation ViewController

@synthesize nameField;
@synthesize companyField;
@synthesize names;
@synthesize companies;
@synthesize existingNames;
@synthesize existingCompanies;
@synthesize tableView1 = _tableView1;
@synthesize tableView2 = _tableView2;

int rowNumber1;
int rowNumber2;

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.names = [[NSMutableArray alloc] init];
    self.companies = [[NSMutableArray alloc] init];
    self.existingNames = [[NSMutableArray alloc] init];
    self.existingCompanies = [[NSMutableArray alloc] init];
    // Do any additional setup after loading the view, typically from a nib.
}

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

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (tableView == self.tableView1){
        return [existingNames count];
    }
    else if (tableView == self.tableView2){
        return [names count];
    }
    return 0;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *simpleTableIdentifier = @"SimpleTableItem";
    UITableViewCell *cell;

    if (tableView == self.tableView1){
        cell = [_tableView1 dequeueReusableCellWithIdentifier:simpleTableIdentifier];
    }
    else if (tableView == self.tableView2){
        cell = [_tableView2 dequeueReusableCellWithIdentifier:simpleTableIdentifier];
    }

    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
    }

    if (tableView == self.tableView1){
        cell.textLabel.text = [existingNames objectAtIndex:indexPath.row];
    }
    else if (tableView == self.tableView2){
        cell.textLabel.text = [names objectAtIndex:indexPath.row];
    }
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
    if (tableView == self.tableView1){
        rowNumber1 = indexPath.row;
    }
    else if (tableView == self.tableView2){
        rowNumber2 = indexPath.row;
    }
}

- (IBAction)add:(id)sender {
    BOOL exists = [existingNames containsObject:nameField.text];

    if(exists == FALSE){
        [names addObject:nameField.text];
        [companies addObject:companyField.text];
        [existingNames addObject:nameField.text];
        [existingCompanies addObject:companyField.text];
    }
    else{
        [names addObject:nameField.text];
        [companies addObject:companyField.text];
    }

    [_tableView1 reloadData];
    [_tableView2 reloadData];

    nameField.text=@"";
    companyField.text=@"";
}

- (IBAction)addExisting:(id)sender {
    [existingNames addObject:[names objectAtIndex:rowNumber1]];
    //[companies addObject:[existingCompanies objectAtIndex:rowNumber]];

    [_tableView2 reloadData];
}

- (IBAction)remove:(id)sender {
    [existingNames removeObjectAtIndex:rowNumber2];
    [existingCompanies removeObjectAtIndex:rowNumber2];

    [_tableView2 reloadData];
}

@end

Answer 1

The following methods are part of the UITableViewDataSource and UITableViewDelegate protocols

tableView:numberOfRowsInSection:
tableView:cellForRowAtIndexPath:
tableView:didSelectRowAtIndexPath:

and will be called by your table view assuming you've property assigned the table view's delegate and dataSource properties. These methods, however,

tableView2:numberOfRowsInSection:
tableView2:cellForRowAtIndexPath:
tableView2:didSelectRowAtIndexPath:

are not part of the protocol and won't ever get called by the table view. It looks like you may be confusing your property names, e.g. tableView, with with the protocol method names, e.g. tableView:numberOfRowsInSection:. What you need to do is:

1. If you haven't already done so, set your view controller as the delegate and dataSource for both your tableView and tableView2.
2. In each of the data source and delegate methods that you need to implement, handle the cases for both tables.

For example, your tableView:numberOfRowsInSection: method would look like:

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (tableView == self.tableView) {
        return [existingNames count];
    }

    else if (tableView == self.tableView2) {
        return [names count];
    }

    return 0;
}