Current User Location return Zero values

Question

I use a global variable (declared as below )for latitude and longitude because i need to use them in other classes in .h class :

extern NSNumber *MYGlobalVariableLat;
extern NSNumber *MYGlobalVariableLong;

Then in .m class:

NSNumber *MYGlobalVariableLat;
NSNumber *MYGlobalVariableLong;

MYGlobalVariableLat = [NSNumber numberWithDouble:[(id)self.mapView.userLocation coordinate].latitude];

MYGlobalVariableLong = [NSNumber numberWithDouble:[mapView.userLocation coordinate].longitude];

NSLog(@"Lat %@",MYGlobalVariableLat);
NSLog(@"Long %@",MYGlobalVariableLong);

that's always print Zero , Any help please ..