I am trying draw route between two location.For that i have two instance of CLLocation startPoin,endPoind. I want to convert this two location two corresponding Location Address.After that i want to fetch all route points from Google map webservice. So did the following code.

- (void)viewDidLoad{
    [super viewDidLoad];
    locations =[[NSMutableArray alloc]initWithCapacity:2];//For location Name 
    [self.mapView_MP setMapType:MKMapTypeStandard];
    [self.mapView_MP setZoomEnabled:YES];
    [self.mapView_MP setScrollEnabled:YES];
    [self update:startPoint];  //MKReverseGeocoder start point  
    [self update:endPoint];    //MKReverseGeocoder end point

    [self updateRoute];

}

- (void)update:(CLLocation*)loc{
    MKReverseGeocoder *geoCoder = [[MKReverseGeocoder alloc] initWithCoordinate:loc.coordinate];


    geoCoder.delegate = self;
    [geoCoder start];

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

    NSMutableDictionary *cplace=[[NSMutableDictionary alloc]initWithDictionary:[placemark addressDictionary]];

   // NSLog(@"The geocoder has returned: %@", [cplace objectForKey:@"FormattedAddressLines"] );
   // NSLog(@"The geocoder has returned: %@", [cplace objectForKey:@"Street"] );
    [locations addObject:[cplace objectForKey:@"SubAdministrativeArea"]];
     NSLog(@"The geocoder has returned: %@", locations );
}
- (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error
{
    NSLog(@"reverseGeocoder:%@ didFailWithError:%@", geocoder, error);
}

- (void)updateRoute {

    self.responseData=[NSMutableData data];  
    NSLog(@" string Formate.................................===%@",locations);   

    NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/directions/json?origin=%@&destination=%@&mode=driving&sensor=false", [locations objectAtIndex:0],[locations objectAtIndex:1]]]];
    [[NSURLConnection alloc] initWithRequest:request delegate:self];    
}

鉴于DidLoad i正在按顺序排列方法。

[self update:startPoint];      //MKReverseGeocoder start point  
    [self update:endPoint];    //MKReverseGeocoder end point           
    [self updateRoute];

but unfortunately [self updateRoute]; is executing first compare to MKReverseGeocoder delegate method. there for the location array is null in side this method. Getting EXEBADACCESS. how can i over come this value. Inside MKReverseGeocoder delegate method i got location name. the Delegate methods is executing any other thread.