Question

Hii all,

i am writting the following code but my application is crashing . I don no why.Actually i want to calculate the speed but app crashes at line no 4 .please explain.debugger says..

Program received signal: “EXC_BAD_ACCESS”.

    - (void)viewDidLoad {
     [super viewDidLoad];



NSDate *date = [NSDate date];
initialDate = date;

              }


  -(void) showSpeed
    {   

[self.initialDate retain];
NSDate *endDate = [NSDate date];

NSTimeInterval  interval = [endDate timeIntervalSinceDate:self.initialDate];

//NSLog(@"time %f",interval);

double speed ;
speed = distance/interval;
NSString *speedValue = [NSString stringWithFormat:@"%1.2f",speed];
     showResult.text = speedValue;

[self.initialDate release];


   }

Answer 1

You probably didn’t retain initialDate when you stored it.

[NSDate date] returns an autoreleased object, and you need to retain it or use a retaining property.

Edit after viewDidLoad code is available:

You need to retain the object that [NSDate date] gives you, because it is autoreleased.

- (void)viewDidLoad {
     [super viewDidLoad];

     initialDate = [[NSDate date] retain];
}

No reason to retain/release it in showSpeed though.

I cannot recommend Apple’s Memory Management Guide enough – it really is essential and worth reading more than once. 🙂