Programmatically filled TableView error - iphone

Question

I get this error when I scroll my table view down:
2012-04-23 09:32:36.763 RedFox[30540:207] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayI objectAtIndex:]: index 12 beyond bounds [0 .. 11]'
*** First throw call stack:
(0x13c3052 0x1554d0a 0x13af674 0x5794 0xb3e0f 0xb4589 0x9fdfd 0xae851 0x59322 0x13c4e72 0x1d6d92d 0x1d77827 0x1cfdfa7 0x1cffea6 0x1cff580 0x13979ce 0x132e670 0x12fa4f6 0x12f9db4 0x12f9ccb 0x12ac879 0x12ac93e 0x1aa9b 0x2158 0x20b5)
terminate called throwing an exceptionsharedlibrary apply-load-rules all
Current language: auto; currently objective-c
An in my .h file I have:
#interface MyTableView : UIViewController <UITableViewDataSource> {
int currentRow;
}
#property (strong,nonatomic) UITableView *tableView;
#property (strong,nonatomic) ViewBuilder *screenDefBuild;
In my .m file:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [screenDefBuild.elementsToTableView count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *MyIdentifier = #"MyIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:MyIdentifier];
}
ScreenListElements *currentScreenElement = [screenDefBuild.elementsToTableView objectAtIndex:currentRow]; //exception points here!
cell.textLabel.text = currentScreenElement.objectName;
currentRow++;
return cell;
}
- (void)viewDidLoad
{
[super viewDidLoad];
tableView = [[UITableView alloc] initWithFrame:self.view.bounds];
[tableView setDataSource:self];
[self.view addSubview:tableView];
}
What's wrong with that?

Answer 1

The currentRow variable is unnecessary and causing issues!
To fix:
change the line
ScreenListElements *currentScreenElement = [screenDefBuild.elementsToTableView objectAtIndex:currentRow]; //exception points here!
to
ScreenListElements *currentScreenElement = [screenDefBuild.elementsToTableView objectAtIndex:indexPath.row]; //exception points here!
Reason:
you increment the currentRow each time cellForARowAtIndexPath: is called, which is wrong, as this method in not only called when displaying following cells(when scrolling down) but also when you scroll up(so currentRow should decrement then). That's why Apple put the parameter indexPath so you can easyily determine which cell tableView is requesting.

Answer 2

The currentRow doesn't really make sense to me.
To return a cell containing a row of your source array (elementsToTableView)
you need to ask for the row in the current index path.
Your error-causing line should look like this:
ScreenListElements *currentScreenElement = [screenDefBuild.elementsToTableView objectAtIndex: indexPath.row];
And you don't need currentRow at all.
Why did you implement it that way?