Question

I need to know where my users are from, so I made a little singleton object which gets the coordinates and uses mapkit to get the country code I need.

Here’s my header file:

#import <Foundation/Foundation.h>
#import <CoreLocation/CoreLocation.h>
#import <MapKit/MapKit.h>

#define TW_GEO_CODER_CHANGED_STATE  @"TW_GEO_CODER_CHANGED_STATE"

@interface TWGeoCoder : NSObject <CLLocationManagerDelegate, MKReverseGeocoderDelegate>
{
    CLLocationManager *locationManager;
    MKReverseGeocoder *geoCoder;

    NSString *currentCountryIsoCode;
}

+ (TWGeoCoder*) sharedTWGeoCoder;

-(void) startGeoCoder;
-(void) stopGeoCoder;


@property (nonatomic, retain) NSString *currentCountryIsoCode;

@end

And the implementation:

#import "TWGeoCoder.h"

@implementation TWGeoCoder


static TWGeoCoder* _singleton;

+ (TWGeoCoder*) sharedTWGeoCoder
{
    @synchronized([TWGeoCoder class])
    {
        if (_singleton == nil)
        {
            _singleton = [[TWGeoCoder alloc] init];
        }
    }
    return _singleton;
}


- (void)startGeoCoder
{  
    if (locationManager == nil) 
    {
        locationManager = [[CLLocationManager alloc] init];
    }
    locationManager.delegate = self;
    locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
    locationManager.distanceFilter = kCLDistanceFilterNone;
    locationManager.purpose = NSLocalizedString(@"#LocalizationPurpose",nil);
    [locationManager startUpdatingLocation];
}

- (void) stopGeoCoder 
{            
    if (geoCoder != nil)
    {
        [geoCoder cancel];
        [geoCoder release];
        geoCoder = nil;
    }

    if (locationManager != nil)
    {
        [locationManager stopUpdatingLocation];
        [locationManager release];
        locationManager = nil;
    }
}


#pragma mark -
#pragma mark locationManager Delegate 

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation 
{
    if (geoCoder == nil)
    {
        geoCoder = [[MKReverseGeocoder alloc] initWithCoordinate:newLocation.coordinate];
    }

    geoCoder.delegate = self;
    [geoCoder start];       
}


- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error 
{
    NSLog(@"locationManager:%@ didFailWithError:%@", manager, error);
    [self stopGeoCoder];
}



#pragma mark -
#pragma mark reverseGeocoder Delegate 

- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark
{

    self.currentCountryIsoCode = placemark.countryCode;

    [[NSNotificationCenter defaultCenter] postNotificationName:TW_GEO_CODER_CHANGED_STATE 
                                                        object:self];
}


- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error
{
    NSLog(@"reverseGeocoder:%@ didFailWithError:%@", geocoder, error);
    [self stopGeoCoder];    
}


#pragma mark -
#pragma mark Synthesizes

@synthesize currentCountryIsoCode;

@end

Well, calling stopGeoCoder method makes my app crash, even calling it via performSelectorOnMainThread…

The problem is in these lines:

if (geoCoder != nil)
    {
        [geoCoder cancel];
        [geoCoder release];
        geoCoder = nil;
    }

It seems like MKReverseGeocoder become really angry when I try to release it!
I get the crash only on the “didFail” method.
Actually, when it finds the placemark, another class will get the notification, does something and call stopGeocoder and… it doesn’t crash!
WTF?

Answer 1

you should refer to another post in stack overflow with the solution:

cllocation and mkreversegeocoder