ViewController segues to MapViewContoller: MapView region wrong first time opened - mkmapview

Question

Good evening,
I'm having problems with an app where a MapView is loaded when a User pushs the Bar Button on a ViewController. The MapViewController gets loaded and the Map shows correct annotations (not shown in source), but the startregion is wrong the first time the App is started and the MapView is opened. When I push the Back button once and reopen the MapView the startregion is fine. It just doesn't work for the first time.
the log gives me the correct values loaded from the plist:
47.572132 and 7.579397
Since I started coding objective-c two weeks ago, please keep your answers as simple as possible ;-)
h.File:
#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>
#import "DetailViewController.h"
#import "Annotation.h"
#interface MapViewController : UIViewController<CLLocationManagerDelegate> {
IBOutlet MKMapView *singlemapview;
}
#property (nonatomic, retain) NSArray *data;
#property int selectedBuilding;
#property (strong, nonatomic) CLLocationManager *location;
#property float longitude;
#property float latitude;
#end
m.File:
#import "MapViewController.h"
#interface MapViewController ()
#end
#implementation MapViewController
#synthesize data;
#synthesize selectedBuilding;
#synthesize location, latitude, longitude;
- (void)viewDidLoad
{
[super viewDidLoad];
NSDictionary *dataItem = [data objectAtIndex:selectedBuilding];
latitude = [[dataItem objectForKey:#"Latitude"] floatValue];
longitude = [[dataItem objectForKey:#"Longitude"] floatValue];
NSLog (#"%f",latitude);
NSLog (#"%f",longitude);
MKCoordinateRegion startregion = { {0.0, 0.0}, {0.0, 0.0} };
startregion.center.latitude = latitude;
startregion.center.longitude = longitude;
startregion.span.latitudeDelta = 0.005;
startregion.span.longitudeDelta = 0.005;
[singlemapview setMapType:MKMapTypeSatellite];
[singlemapview setZoomEnabled:YES];
[singlemapview setScrollEnabled:YES];
[singlemapview addAnnotation:singlebuilding];
[singlemapview setRegion:startregion];
}

Answer 1

My app had exactly the same behavior when calling setRegion method in viewDidLoad or viewWillAppear. but, calling it in viewDidAppear corrected the problem. hope this helps.

Answer 2

I could solve my problem now through using the -(void)viewWillAppear:(BOOL)animated function instead of using -(void)viewDidLoad
As i understand now:
ViewDidLoad is called once before a new view is opened (before the segue animation starts). But it is however still too late to draw the map correctly.
ViewDidAppear is called every time after a view did appear on the screen (after the segue animation is over).
ViewWillApper is called and calculated totally before a new view is opened (before segue animation). That's why it works properly when you have a map.