Question

I am trying to understand the crash log. It happens when I try to perform the CLLocationDistance method distanceFromLocation. In order to get two locations I need to geocode, but I need one block so I can have those two instance variables. So I direct it to a method with parameters:

  - (void)geoCodeSetup:(NSArray *)placemarks :(NSError *)error andIdentifier:(NSString *)string {
CLLocation *location1;
CLLocation *location2;
if ([string isEqualToString:@"Origin"]) {
    if (!error) {
        CLPlacemark *place = [placemarks objectAtIndex:0];
        CLLocation *location = place.location;
        location1 = [[CLLocation alloc] initWithLatitude:location.coordinate.latitude longitude:location.coordinate.longitude];

    } else {
        NSString *string = [NSString stringWithFormat:@"%@ - also make sure you have inputted a valid city", [error localizedDescription]];
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:string delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
        [alert show];
    }
}

if ([string isEqualToString:@"Destination"]) {
    if (!error) {
        CLPlacemark *place = [placemarks objectAtIndex:0];
        CLLocation *location = place.location;
       location2 = [[CLLocation alloc] initWithLatitude:location.coordinate.latitude longitude:location.coordinate.longitude];


    } else {
        NSString *string = [NSString stringWithFormat:@"%@ - also make sure you have inputted a valid city", [error localizedDescription]];
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:string delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil];
        [alert show];
    }
}


CLLocationDistance distanceM = [location1 distanceFromLocation:location2];    
[metreDistance setText:[NSString stringWithFormat:@"%f", distanceM]];

}

- (IBAction)calculateDistance {

[textFieldDestination resignFirstResponder];
NSString *origin = [textFieldOrigin text];
if (origin) {
    CLGeocoder *geoCode = [[CLGeocoder alloc] init];

    [geoCode geocodeAddressString:origin completionHandler: ^(NSArray *placemarks, NSError *error) {
        NSArray *p1 = placemarks;
        NSError *e1 = error;
        [p1 retain];
        [e1 retain];
        [self geoCodeSetup:p1 :e1 andIdentifier:@"Origin"];


    }]; 
}

NSString *destination = [textFieldDestination text];
if (destination) {

    CLGeocoder *geoCode2 = [[CLGeocoder alloc] init];

    [geoCode2 geocodeAddressString:destination completionHandler:^(NSArray *placemarks, NSError *error) {
        NSArray *p2 = placemarks;
        NSError *e2 = error;
        [p2 retain];
        [e2 retain];
        [self geoCodeSetup:p2 :e2 andIdentifier:@"Destination"];




    }]; 
}

It crashes/gives EXC_BAD_ACCESS (code =EXC_ARM_DA_ALIGN, address=.....etc....) on the distanceFromLocation part. I have attached a screenshot of the crash log.

What might cause this and how do I solve it?

Answer 1

I assume that location1 or location2 is not set because you did wrap it into

if ([string isEqualToString:@"Origin"]) {
    if (!error) {

You might avoid the crash by chaining line 2 and 3 to:

CLLocation *location1 = nil;
CLLocation *location2 = nil;

and maybe you need also to change line:

CLLocationDistance distanceM = [location1 distanceFromLocation:location2]; 
// change to
CLLocationDistance distanceM;
if(location1 && location2) {
  distanceM = [location1 distanceFromLocation:location2];
}

i think you run distanceFromLocation: with at least one NULL parameter or object.