IBAction方法中的应用崩溃

Question

Okay, so here is my code

-(IBAction)nextAction
{
    dispatch_async(myQueue, ^{ [self plusOneDate]; });
}

-(void)plusOneDate
{
    int hoursToAdd = 1;  

    // set up date components
    NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
    [components setHour:hoursToAdd];

    // create a calendar
    NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
    NSDate *newDate2 = [gregorian dateByAddingComponents:components toDate:appStateDate options:0];

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    [formatter setDateFormat:@"YYYYMMddHH0000"];
    dateString = [formatter stringFromDate:newDate2];
    [formatter release];

    appStateDate = newDate2;
    newDate2 = nil;
}

All it does is it adds 1 hour to a NSDate object (appStateDate), formats it, and sets the dateString variable.

Every time I press the UIButton in the app, connected to nextAction , the app crashes. I tried deleting the xib file and creating a new one. It did not help, and still crashes.

In debug mode:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '(null): unrecognized selector sent to class 0x6242690'

Anyone who know why? I'm getting frustrated.

Answer 1

This isn't an answer so much as it is an observation. The value assigned to appStateDate at the end of the method is an autoreleased object, and nowhere are you retaining it. You cannot rely on the "retain" attribute of the property (if appStateDate is in fact declared as a property somewhere), because you didn't use the property in the assignment.

As soon as that IBAction finishes, the object pointed to by appStateDate is going to be reclaimed when the runloop drains the NSAutoreleasePool. Perhaps that's where the crash is coming from.