Question

why do I need this autorelease after [NSMutableArray array] to avoid a memory leak?

That is Instruments told me there was a leak. By putting the autorelease in it solved it, however I’m not sure why this would be required. The “array” method wasn’t like an INIT or COPY etc…

@interface Weekend : NSObject {
    NSMutableArray*     _events;     
}
@property (nonatomic, retain) NSMutableArray* events;
@end

@implementation Weekend

@synthesize events = _events;

- (id)init {
    if (self == [super init])
    {
        self.events = [[NSMutableArray array] autorelease];    // WHY IS THIS AUTORELEASE REQUIRED
    }
    return self;
}

- (void) dealloc {
    [_events release];  _events = nil;
    [super dealloc];
}

@end

NOTE: This is what I see in Intruments when I take autorelease out (and after I changed the “if (self == [super init])” to “if ((self = [super init]))”

#  Category     Event        Code Location
0  __NSArrayM   Malloc       at the [NSMutableArray array] point
1  __NSArrayM   Autorelease  at the [NSMutableArray array] point
2  __NSArrayM   Retain       at the @synthesize events = _events; point of the code
3  __NSArrayM   Release      QuartzCore - CA:Transaction::observer_callback(__CF........)
                             (from main.m:14 - "int retVal = UIApplicationMain(argc, argv, nil, nil);")

Answer 1

Why do you need that extra release? You don’t. Not there, anyway.

The problem is you’re overretaining _events somewhere else. Maybe you’re passing it to another class that’s retaining without releasing? Leaks are always attributed by Instruments to creation of the object, not the unbalanced retain.

Adding that autorelease instead of finding the unbalanced retain is the memory management equivalent of having an answer that’s off by 0.3 and just adding 0.3 to fix it. You need to remove that and fix the real problem.

Edit: After reading your latest edit, I think you’ll probably find that Weekend itself is being leaked.