Question

I would like to ask about memory management with regards to MKReverseGeocoder, prior to iOS4.3 I had been using the code below, allocing MKReverseGeocoder and then releasing it in either reverseGeocoder:didFindPlavemark or reverseGeoCoder:didFailWithError as appropriate.

However with iOS4.3 I am getting EXC_BAD_ACCESS and it seems to be coming from the release in reverseGeocoder:didFailWithError. I would very much appreciate it if someone could point me in the right direction, could I use autoRelease, would that alloc the geoCoder to hang around long enough for the delegate to do its work?

// ALLOC & START
MKReverseGeocoder *myGeocoder = [[MKReverseGeocoder alloc] initWithCoordinate:[lastGoodLocation coordinate]];
[myGeocoder setDelegate:self];
[myGeocoder start];

.

// DID FIND
- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark {
    NSLog(@"GEOCODE: didFindPlacemark");
    [self createLocation:placemark];
    [geocoder release];
}

.

// DID FAIL
- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error {
    NSLog(@"GEOCODE: didFailWithError");
    [self createLocation:nil];
    [geocoder release];
}

Answer 1

After a little searching, I think the solution might be to setup an iVar to hold the MKReverseGeocoder. This way I can use autorelease whilst still being sure that the iVar will hold onto the geoCoder until the next time the iVar is set. Interestingly enough the code above only produces an EXC_BAD_ACCESS from reverseGeocoder:didFailWithError, not from reverseGeocoder:didFindPlacemark. I also checked the retain counts (yes I know its not reliable but I wanted to look) and before the release (that crashes) both methods report a retain count of 1. The only thing I can guess is that the geocoded object might still be being used somewhere when I do the release. It also feels messy allocing in one method and releasing using a pointer from the callback.

@property(nonatomic, retain)MKReverseGeocoder geoCoder;

.

[self setGeoCoder:[[[MKReverseGeocoder alloc] initWithCoordinate:coord] autorelease]];
[[self geoCoder] setDelegate:self];
[[self geoCoder] start];