My cut down version of INTULocationManager does not work - ios

Question

I have an iPhone hybrid app using INTULocationManager that works well but the software is far more than I need. I have cut down to the basics as far as I can see, but I have obviously got something wrong when trying to invoke the callback to the block saved when the location request. Please can someone spot the probably pretty obvious error for me.
My .h file for this is
#import <Foundation/Foundation.h>
#import <CoreLocation/CoreLocation.h>
typedef void(^SBLocationRequestBlock)(CLLocation *currentLocation);
#interface SBLocationManager : NSObject
// Returns the singleton instance of this class.
+ (instancetype)sharedInstance;
// Creates a subscription for location updates
- (void)subscribeToLocationUpdatesWithBlock:(SBLocationRequestBlock)block;
// Set the minimum distance between two successive location returns
- (void)setDistanceFilter:(double)distance;
#end
My .m file is as follows
#import "SBLocationManager.h"
#import "SBLocationManager+Internal.h"
#interface SBLocationManager () <CLLocationManagerDelegate>
// The instance of CLLocationManager encapsulated by this class.
#property (nonatomic, strong) CLLocationManager *locationManager;
// Whether or not the CLLocationManager is currently sending location updates.
#property (nonatomic, assign) BOOL isUpdatingLocation ;
//Whether an error occurred during the last location update.
#property (nonatomic, assign) BOOL updateFailed;
// the code to be called when a location is available
#property (nonatomic, assign) SBLocationRequestBlock block;
#end
#implementation SBLocationManager
static id _sharedInstance;
// Create instance of this class.
- (instancetype)init
{
//self = [super init];
if (self) {
_locationManager = [[CLLocationManager alloc] init];
_locationManager.delegate = self;
_locationManager.pausesLocationUpdatesAutomatically = NO; // to keep it going in background mode
#ifdef __IPHONE_8_4
#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_8_4
/* iOS 9 requires setting allowsBackgroundLocationUpdates to YES in order to receive background location updates.
We only set it to YES if the location background mode is enabled for this app, as the documentation suggests it is a
fatal programmer error otherwise. */
NSArray *backgroundModes = [[NSBundle mainBundle] objectForInfoDictionaryKey:#"UIBackgroundModes"];
if ([backgroundModes containsObject:#"location"]) {
if ([_locationManager respondsToSelector:#selector(setAllowsBackgroundLocationUpdates:)]) {
[_locationManager setAllowsBackgroundLocationUpdates:YES];
}
}
#endif /* __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_8_4 */
#endif /* __IPHONE_8_4 */
}
self.isUpdatingLocation = NO ;
return self;
}
+ (instancetype)sharedInstance
{
static dispatch_once_t _onceToken;
dispatch_once(&_onceToken, ^{
_sharedInstance = [[self alloc] init];
});
return _sharedInstance;
}
- (void)subscribeToLocationUpdatesWithBlock:(SBLocationRequestBlock)block
{
self.block = block;
[self requestAuthorizationIfNeeded];
[self.locationManager startUpdatingLocation];
self.isUpdatingLocation = YES;
}
- (void)setDistanceFilter:(double)distance
{
self.locationManager.distanceFilter = distance ;
self.locationManager.desiredAccuracy = distance ;
}
#pragma mark Internal methods
//Requests permission to use location services on devices with iOS 8+.
- (void)requestAuthorizationIfNeeded
{
#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_7_1
// As of iOS 8, apps must explicitly request location services permissions
// SBLocationManager supports both levels, "Always" and "When In Use".
// SBLocationManager determines which level of permissions to request based
// which description key is present in your app's Info.plist
// If you provide values for both description keys, the more permissive "Always
// level is requested.
if (floor(NSFoundationVersionNumber) > NSFoundationVersionNumber_iOS_7_1 && [CLLocationManager authorizationStatus] == kCLAuthorizationStatusNotDetermined) {
BOOL hasAlwaysKey = [[NSBundle mainBundle] objectForInfoDictionaryKey:#"NSLocationAlwaysUsageDescription"] != nil;
BOOL hasWhenInUseKey = [[NSBundle mainBundle] objectForInfoDictionaryKey:#"NSLocationWhenInUseUsageDescription"] != nil;
if (hasAlwaysKey) {
[self.locationManager requestAlwaysAuthorization];
} else if (hasWhenInUseKey) {
[self.locationManager requestWhenInUseAuthorization];
} else {
// At least one of the keys NSLocationAlwaysUsageDescription
// NSLocationWhenInUseUsageDescription MUST be present in the Info.plis
// file to use location services on iOS 8+.
NSAssert(hasAlwaysKey || hasWhenInUseKey, #"To use location services in iOS 8+, your Info.plist must provide a value for either NSLocationWhenInUseUsageDescription or NSLocationAlwaysUsageDescription.");
}
}
#endif /* __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_7_1 */
}
#pragma mark CLLocationManagerDelegate methods
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
self.updateFailed = NO;
CLLocation *mostRecentLocation = [locations lastObject];
dispatch_async(dispatch_get_main_queue(), ^{
if (self.block) {
self.block(mostRecentLocation);
}
});
}
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
self.updateFailed = YES;
}
- (void)locationManager:(CLLocationManager *)manager didChangeAuthorizationStatus:(CLAuthorizationStatus)status
{
}
#end
I invoke the request as follows :
- (void)requestLocationUpdates:(double)distanceValue
{
SBLocationManager *locMgr = [SBLocationManager sharedInstance];
[locMgr subscribeToLocationUpdatesWithBlock:^(CLLocation *currentLocation) {
NSLog (#"New Location:\n%#", currentLocation);
NSString *javascriptString = [NSString stringWithFormat:#"UpdateOwnLocation('%.6f','%.6f','%.6f');", currentLocation.coordinate.latitude, currentLocation.coordinate.longitude, currentLocation.horizontalAccuracy];
[webView stringByEvaluatingJavaScriptFromString:javascriptString];
}];
[locMgr setDistanceFilter:distanceValue];
}
- (void) changeLocationUpdates:(double)distanceValue
{
SBLocationManager *locMgr = [SBLocationManager sharedInstance];
[locMgr setDistanceFilter:distanceValue];
}
However when I run this (in the simulator) I get
EXC_BAD_ACCESS in the line self.block (mostRecentLocation).
i.e. the location manager is setup and returns a location but my code for calling the requesting block fails. I have noted in the debugger that self.block is correctly pointing at my view controller code when in subscribeToLocationUpdatesWithBlock but by the time the code gets to invoking the block on the main queue it points somewhere else. Is this because self is no longer the same in this bit of code.
My apologies for bad terminology, I am a javascript programmer attempting to do something with XCode that is probably beyond my skills. Any help anyone can provide would be lovely.

Answer 1

I would use copy, not assign for the block property. assign is for simple things like int usually.
To narrow down if it's the block or location, add an NSLog for mostRecentLocation before calling the block.
If that's not it, check out my blog post on debugging EXC_BAD_ACCESS:
http://loufranco.com/blog/understanding-exc_bad_access