Question

For some reason whenever i click on my pin the app crashes. there are no errors or warnings in my code. It only happens when i try to get the distance from userLocation to the pin. find my mistake?

@implementation FirstViewController
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
{   
mapView.showsUserLocation = YES;

[super viewDidLoad];
}
-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation   { 

[self showPin];
[self updateLocation];
}
-(IBAction) updateLocation{
mapView.showsUserLocation = YES;
}
 - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}  


- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];

// Release any cached data, images, etc. that aren't in use.
}


- (void)viewDidUnload
{
[super viewDidUnload];

// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}


-(IBAction)setMap:(id)sender{
switch(((UISegmentedControl *)sender).selectedSegmentIndex){
case 0:
{
    mapView.mapType = MKMapTypeStandard;
     break;
}
case 1:
{
    mapView.mapType = MKMapTypeSatellite;
    break;
}
case 2:
{
mapView.mapType = MKMapTypeHybrid;
break;
}

}}
- (void)dealloc
{
[super dealloc];
}
- (MKAnnotationView *)mapView:(MKMapView *)mv viewForAnnotation:(id <MKAnnotation>)annotation {
MKPinAnnotationView *pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:@"pinView"];
if (!pinView) {
    pinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"pinView"] autorelease];
    pinView.pinColor = MKPinAnnotationColorRed;
    pinView.animatesDrop = YES;
    pinView.canShowCallout = YES;


    UIButton *rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
    pinView.rightCalloutAccessoryView = rightButton;
} else {
    pinView.annotation = annotation;
}
if (annotation == mapView.userLocation){
    return nil; //default to blue dot
}
return pinView;
}
-(IBAction) showPin{
//MOST CODE WILL BE INSERTED HERE!
//instructions

CLLocation *usersLocation = [[CLLocation alloc]initWithLatitude:mapView.userLocation.coordinate.latitude longitude:mapView.userLocation.coordinate.longitude];
MKCoordinateRegion region;
MKCoordinateSpan span;
span.latitudeDelta=0.2;
span.longitudeDelta=0.2;
//ignore above
//always declare location as companyCity 
//if more than one in one city then add a number i.e. companyCity2
//chili in mobile alabama
CLLocationCoordinate2D chiliAuburn = mapView.userLocation.coordinate;

chiliAuburn.latitude = 32.606434 ;
chiliAuburn.longitude = -85.484025;
region.span=span;
region.center=chiliAuburn;
CLLocation *chiliAuburnLocation = [[CLLocation alloc] initWithLatitude:chiliAuburn.latitude longitude:chiliAuburn.longitude];
if(chiliAuburnAlabama != nil) {
    [mapView removeAnnotation:chiliAuburnAlabama];
    [chiliAuburnAlabama release];
    chiliAuburnAlabama = nil;
}

chiliAuburnAlabama = [[AddressAnnotation alloc] initWithCoordinate:chiliAuburn];
[chiliAuburnAlabama setTitle:@"Chili Yogurt Café"];
double distanceMiles = ([usersLocation distanceFromLocation:chiliAuburnLocation]/1609.334);
[chiliAuburnAlabama setSubTitle:[NSString stringWithFormat:@"%.2fm", distanceMiles]];
//[chiliAuburnAlabama setSubTitle:@"TEST"];
[mapView addAnnotation:chiliAuburnAlabama];
[chiliAuburnAlabama release];
//tutti frutti homewood alabama
CLLocationCoordinate2D tuttifruttiHomewood = mapView.userLocation.coordinate;

tuttifruttiHomewood.latitude = 33.479775 ;
tuttifruttiHomewood.longitude = -86.790977;
region.span=span;
region.center=tuttifruttiHomewood;

if(tuttifruttiHomewoodAlabama != nil) {
    [mapView removeAnnotation:tuttifruttiHomewoodAlabama];
    [tuttifruttiHomewoodAlabama release];
    tuttifruttiHomewoodAlabama = nil;
}

tuttifruttiHomewoodAlabama = [[AddressAnnotation alloc] initWithCoordinate:tuttifruttiHomewood];
[tuttifruttiHomewoodAlabama setTitle:@"Tutti Frutti"];
[tuttifruttiHomewoodAlabama setSubTitle:@"YOUR RATING HERE"];
[mapView addAnnotation:tuttifruttiHomewoodAlabama];


//ignore below
[mapView setRegion:region animated:TRUE];
[mapView regionThatFits:region];

}
- (void)mapView:(MKMapView *)mv didAddAnnotationViews:(NSArray *)views {
for(MKAnnotationView *annotationView in views) {
    if(annotationView.annotation == mv.userLocation) {
        MKCoordinateRegion region;
        MKCoordinateSpan span;

        span.latitudeDelta=0.1;
        span.longitudeDelta=0.1; 

        CLLocationCoordinate2D location=mv.userLocation.coordinate;

        region.span=span;
        region.center=location;

        [mv setRegion:region animated:TRUE];
        [mv regionThatFits:region];
    }

}
}



@end

GNU gdb 6.3.50-20050815 (Apple version gdb-1518) (Sat Feb 12 02:52:12 UTC 2011)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type “show copying” to see the conditions.
There is absolutely no warranty for GDB. Type “show warranty” for details.
This GDB was configured as “x86_64-apple-darwin”.Attaching to process 23386.
2011-06-02 00:39:46.146 YogurtStoreLocator[23386:207] 32.606434,-85.484025
2011-06-02 00:39:46.148 YogurtStoreLocator[23386:207] 33.479775,-86.790977
2011-06-02 00:39:53.121 YogurtStoreLocator[23386:207] -[NSCFNumber stringByStandardizingWhitespace]: unrecognized selector sent to instance 0x587b2d0
2011-06-02 00:39:53.123 YogurtStoreLocator[23386:207] * Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘-[NSCFNumber stringByStandardizingWhitespace]: unrecognized selector sent to instance 0x587b2d0’
* Call stack at first throw:
(
0 CoreFoundation 0x00fca5a9 exceptionPreprocess + 185
1 libobjc.A.dylib 0x0111e313 objc_exception_throw + 44
2 CoreFoundation 0x00fcc0bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3 CoreFoundation 0x00f3b966 __forwarding + 966
4 CoreFoundation 0x00f3b522 _CF_forwarding_prep_0 + 50
5 UIKit 0x0034c340 -[UICalloutView setSubtitle:animated:] + 88
6 UIKit 0x0034c010 -[UICalloutView setSubtitle:] + 49
7 MapKit 0x000bb0ac -[MKAnnotationContainerView _showBubbleForAnnotationView:bounce:scrollToFit:userInitiated:avoid:] + 537
8 MapKit 0x000bc3ed -[MKAnnotationContainerView _setSelectedAnnotationView:bounce:pressed:scrollToFit:userInitiated:avoid:] + 653
9 MapKit 0x000b54bc -[MKAnnotationContainerView _setSelectedAnnotationView:bounce:pressed:scrollToFit:userInitiated:] + 144
10 MapKit 0x0008cab3 -[MKMapView handleTap:] + 459
11 UIKit 0x004ad4f2 -[UIGestureRecognizer _updateGestureWithEvent:] + 730
12 UIKit 0x004a94fe -[UIGestureRecognizer _delayedUpdateGesture] + 47
13 UIKit 0x004afafc _UIGestureRecognizerUpdateObserver + 584
14 CoreFoundation 0x00fab89b CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 27
15 CoreFoundation 0x00f406e7 __CFRunLoopDoObservers + 295
16 CoreFoundation 0x00f091d7 __CFRunLoopRun + 1575
17 CoreFoundation 0x00f08840 CFRunLoopRunSpecific + 208
18 CoreFoundation 0x00f08761 CFRunLoopRunInMode + 97
19 GraphicsServices 0x01f071c4 GSEventRunModal + 217
20 GraphicsServices 0x01f07289 GSEventRun + 115
21 UIKit 0x0022ac93 UIApplicationMain + 1160
22 YogurtStoreLocator 0x00002099 main + 121
23 YogurtStoreLocator 0x00002015 start + 53
)
terminate called after throwing an instance of ‘NSException’
sharedlibrary apply-load-rules all
Current language: auto; currently objective-c
(gdb)

Answer 1

Just setting showsUserLocation to YES isn’t sufficient. The map view needs to fetch that data. This is an asynchronous process and the data will be updated only after a while. The delegate is notified of this update via mapView:didUpdateUseLocation: method. You should implement that method and make a call to showPin only after you’ve the user location.