Question

I am trying to do the following:

1) user clicks button start, it runs startTimer method, which sets a new [NSDate date].

2) user clicks button stop it runs stopTimer method, which retrieves the [NSDate date] value.

I can’t get step number 2 working. I’ve set it in the .h file. If I copy the code from the start method into the stop method it works. So, I can set the [NSDate date]. But, this is not what I want. I want to be able to set it in the startTimer method. How do i go about this?

.h file

@interface StartTest : UIViewController {
    IBOutlet UILabel *timer;

    NSDate *startNSDate;
    NSDate *start;



}

- (IBAction)startTimer;
- (IBAction)stopTimer;

- (NSDate *)setStart;
- (NSDate *)getStart;


@end

.m file:

@implementation Ash

- (IBAction)startTimer {

    startNSDate = [NSDate date];

}


- (IBAction)stopTimer{

    start = [NSDate date];


    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy"];


    NSString *stringFromDate = [formatter stringFromDate:startNSDate]; // <<< this is where it fails

    NSLog(@"stringfromdate: %@", stringFromDate);
}

Answer 1

startNSDate isn’t retained and by the time you want to access it, it’s already dealloc’d, hence you’re trying to access garbage pointer

easiest solution for you will be

@interface StartTest : UIViewController {
    IBOutlet UILabel *timer;

    NSDate *startNSDate;
    NSDate *start;



}
@property (nonatomic, strong) NSDate* startNSDate;

- (IBAction)startTimer;
- (IBAction)stopTimer;

- (NSDate *)setStart;
- (NSDate *)getStart;


@end




@implementation Ash

- (IBAction)startTimer {

    self.startNSDate = [NSDate date];

}


- (IBAction)stopTimer{

    start = [NSDate date];


    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy"];

    // this is where it fails, the reason being that startNSDate isn't retained
    // and by this line, it's already dealloc'd, hence you're trying to access
    // garbage pointer
    NSString *stringFromDate = [formatter self.startNSDate]; 

    NSLog(@"stringfromdate: %@", stringFromDate);
}

- (void)dealloc
{
    self.startNSDate = nil;
    [super dealloc];
}