'NSRangeException' while reading data from a file - iphone

Question

I am trying to save data when the home button is pressed.
Here is my relevant code.
- (NSString *) saveFilePath
{
NSArray *path =
NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
return [[path objectAtIndex:0] stringByAppendingPathComponent:#"savefile.plist"];
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
NSArray *values = [[NSArray alloc] initWithObjects:
[NSNumber numberWithInt:askedQuestions], //for questionLabel
[NSNumber numberWithInt:timeMin], //timeMin
[NSNumber numberWithInt:timeSec], //timeSec
[NSNumber numberWithInt:skipCount], //skipped question
[NSNumber numberWithInt:correctAnswers], //corectAnswers
nil];
[values writeToFile:[self saveFilePath] atomically:YES];
}
saveFilePath method is providing the file path.
And in viewDidLoad
NSString *myPath = [self saveFilePath];
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:myPath];
if (fileExists)
{
NSArray *values = [[NSArray alloc] initWithContentsOfFile:myPath];
_readerLabel.text = [[values objectAtIndex:0] stringValue];
askedQuestions=[[values objectAtIndex:0] intValue];
timeMin=[[values objectAtIndex:1]intValue];
timeSec=[[values objectAtIndex:2]intValue];
skipCount=[[values objectAtIndex:3]intValue];
correctAnswers=[[values objectAtIndex:4]intValue];
}
UIApplication *myApp = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationDidEnterBackground:)
name:UIApplicationDidEnterBackgroundNotification
object:myApp];
and i am getting this:
Terminating app due to uncaught exception 'NSRangeException', reason: '-[__NSCFArray objectAtIndex:]: index (0) beyond bounds (0)'
*** First throw call stack:
(0x16a1012 0x13aee7e 0x16a0deb 0x16957e0 0x6891 0x312d 0x305817 0x305882 0x254a25 0x254dbf 0x254f55 0x25df67 0x221fcc 0x222fab 0x234315 0x23524b 0x226cf8 0x2703df9 0x2703ad0 0x1616bf5 0x1616962 0x1647bb6 0x1646f44 0x1646e1b 0x2227da 0x22465c 0x26cd 0x25f5)
libc++abi.dylib: terminate called throwing an exception
Where is the problem in the code. Please help!

Answer 1

You're not checking to see if anything has worked!
What happens if
NSArray *values = [[NSArray alloc] initWithContentsOfFile:myPath];
either fails (the file might not exist) or if it returns an array with 0 items in?
You need to add something like :
NSArray *values = [[NSArray alloc] initWithContentsOfFile:myPath];
if (values.count > 0) {
...
}
You should also set a breakpoint on applicationDidEnterBackground: and step though to make sure that your save method is working as you expect.
Also, I suspect one of these two lines is wrong :
_readerLabel.text = [[values objectAtIndex:0] stringValue];
askedQuestions=[[values objectAtIndex:0] intValue];
they're both asking for the item at index 0