Objective C - -[__NSCFString _isAncestorOfFirstResponder] Error - ios

Question

I'm trying to create this application, when you press on a tablecell you get shown the ViewController, and the variable get's set in the other view controller. Although i'm getting a few errors when i press the uitablecell.
Error:
2013-04-06 22:47:25.970 iFSX Guide[1069:907] Called
2013-04-06 22:47:26.009 iFSX Guide[1069:907] -[__NSCFString _isAncestorOfFirstResponder]: unrecognized selector sent to instance 0x1d562390
2013-04-06 22:47:26.016 iFSX Guide[1069:907] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString _isAncestorOfFirstResponder]: unrecognized selector sent to instance 0x1d562390'
*** First throw call stack:
(0x319b22a3 0x3964c97f 0x319b5e07 0x319b4531 0x3190bf68 0x33832beb 0x338a837f 0x338548fb 0x33a95619 0x338a79b9 0x338a5fe7 0x339c83ef 0xa22a5 0x3387c28d 0x338fef81 0x322c0277 0x319875df 0x31987291 0x31985f01 0x318f8ebd 0x318f8d49 0x354ba2eb 0x3380e301 0xa19d1 0x39a83b20)
libc++abi.dylib: terminate called throwing an exception
The code:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)in dexPath{
NSLog(#"Called");
Aircraft = indexPath.row;
[self performSegueWithIdentifier:#"ToSections" sender:self];
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if([segue.identifier isEqualToString:#"ToSections"]){
AirplaneSections *sections = (AirplaneSections *)segue.destinationViewController;
sections.plane = Aircraft;
}
}
I've found out that it's an error on ViewDidLoad on the viewcontroller.
NSString *quickTemp = [NSString alloc];
switch (plane) {
case 0:
quickTemp = #"Boeing 737-800";
break;
default:
break;
}
TitleLabel.text = quickTemp;
*/
I'm doing something wrong there.

Answer 1

Are you using ARC? This sort of problem usually indicates there's a memory error somewhere. Basically, some code somewhere is trying to access an object that was already released. This makes everything go kaboom.
If you aren't using ARC, you should turn it on.
After that, the next thing you should do is run the static analyzer. Fix anything that comes up.
If that doesn't fix the problem, in Xcode, add a breakpoint that stops when an Objective-C exception is thrown. It should show you where exactly this problem is happening.
If that doesn't help, run your code under Instruments' and the Zombie tool. This will show you exactly where you tried to access memory that was already released.