Question

I’m working through Cocoa Programming for Mac OS X (3rd ed) and in chapter 4 I wrote this app:

int main (int argc, const char * argv[]) {     NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];      //create the date object     NSCalendarDate *now = [[NSCalendarDate alloc] init];      //seed random # generator     srandom(time(NULL));      NSMutableArray *array;     array = [[NSMutableArray alloc] init];     int i;     for (i=0; i<10; i++){         //create a date/time that is 'i' weeks from now         NSCalendarDate *iWeeksFromNow;         iWeeksFromNow = [now dateByAddingYears:0                                         months:0                                           days:(i*7)                                          hours:0                                        minutes:0                                        seconds:0];          //create a new instance of lottery entry         LotteryEntry *entry = [[LotteryEntry alloc] init];         [entry setEntryDate:iWeeksFromNow];          [array addObject:entry];         [entry release];     }     [now release];     now = nil;      for (LotteryEntry *entryToPrint in array) {         NSLog(@'%@', entryToPrint);     }     [array release];     array = nil;      NSLog(@'about to drain the pool... (%@)', pool);     [pool drain];     NSLog(@'done');     NSLog(@'GC = %@', [NSGarbageCollector defaultCollector]);     return 0; } 

The LotteryEntry class looks like this:

@implementation LotteryEntry  - (void)setEntryDate:(NSCalendarDate *)date {     entryDate = date; }  - (NSCalendarDate *)entryDate {     return entryDate; }  - (int)firstNumber {     return firstNumber; }  - (int)secondNumber {     return secondNumber; }  - (id)init {     return [self initWithDate:[NSCalendarDate calendarDate]]; }  - (id)initWithDate:(NSCalendarDate *)date {     if(![super init])         return nil;      NSAssert(date != nil, @'Argument must be non-nil');      firstNumber = random() % 100 + 1;     secondNumber = random() % 100 + 1;     entryDate = [date retain];       return self; }  - (NSString *)description {     NSString *result;     result = [[NSString alloc] initWithFormat:@'%@ = %d and %d',               [entryDate descriptionWithCalendarFormat:@'%b %d %Y'],               firstNumber,               secondNumber];     return result; }  - (void)dealloc {     NSLog(@'deallocating %@', self);     [entryDate release];     [super dealloc]; }  @end 

As you can see I’m retaining and releasing the objects here. I’m pretty sure my code matches the book’s, however when I run the app, at the [pool drain] I get this message:

Program received signal: “EXC_BAD_ACCESS”.

I’m not sure what’s causing this. I’m hoping it’s something stupid that I missed, but I’d sure appreciate a few other pairs of eyes on it. Thanks in advance!

(side note: I’m a .NET developer, so ref counting is pretty foreign to me!)

Answer 1

doh! Just typing the code made me realize my problem. Doncha love it when that happens?

I am retaining the date in my init, but I still had that extra setEntryDate method that was not calling retain. Removing this and calling the initWithDate method instead seemed to fix the problem.