objective-c MKMapView center on user location - ios

Question

I'm trying to zoom into the user location as the center reference for the screen. I have this code:
MainViewController.h
#import <UIKit/UIKit.h>
#import "FlipsideViewController.h"
#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>
IBOutlet MKMapView *mapView;
#interface MainViewController : UIViewController <FlipsideViewControllerDelegate, MKMapViewDelegate> {
MKMapView *mapView;
}
#property (nonatomic, retain) IBOutlet MKMapView *mapView;
MainViewController.m
#implementation MainViewController
#synthesize mapView;
- (void)viewDidLoad {
[super viewDidLoad];
mapView = [[MKMapView alloc]
initWithFrame:self.view.bounds
];
mapView.showsUserLocation = YES;
mapView.mapType = MKMapTypeHybrid;
mapView.delegate = self;
[self.view addSubview:mapView];
}
- (void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation {
MKCoordinateRegion region;
MKCoordinateSpan span;
span.latitudeDelta = 0.005;
span.longitudeDelta = 0.005;
CLLocationCoordinate2D location;
location.latitude = userLocation.coordinate.latitude;
location.longitude = userLocation.coordinate.longitude;
region.span = span;
region.center = location;
[mapView setRegion:region animated:YES];
}
Now I'm only getting a build warning on the last line [mapView setRegion:region animated:YES] stating: 'local declaration of 'mapView' hides instance variable'

Answer 1

When you do mapView.showsUserLocation = YES;, you ask it to retrieve the user location. This doesn't happen instantly. As it takes time, the map view notifies its delegate that a user location is available via the delegate method mapView:didUpdateUserLocation. So you should adopt the MKMapViewDelegate protocol and implement that method. You should move all your zooming-in code to this method.
Setting the delegate
- (void)viewDidLoad {
[super viewDidLoad];
mapView = [[MKMapView alloc]
initWithFrame:CGRectMake(0,
0,
self.view.bounds.size.width,
self.view.bounds.size.height)
];
mapView.showsUserLocation = YES;
mapView.mapType = MKMapTypeHybrid;
mapView.delegate = self;
[self.view addSubview:mapView];
}
Updated delegate method
- (void)mapView:(MKMapView *)aMapView didUpdateUserLocation:(MKUserLocation *)aUserLocation {
MKCoordinateRegion region;
MKCoordinateSpan span;
span.latitudeDelta = 0.005;
span.longitudeDelta = 0.005;
CLLocationCoordinate2D location;
location.latitude = aUserLocation.coordinate.latitude;
location.longitude = aUserLocation.coordinate.longitude;
region.span = span;
region.center = location;
[aMapView setRegion:region animated:YES];
}

Answer 2

In your interface you forgot to inherit MapViewDelegate -
#import <MapKit/MapKit.h>
#interface MainViewController : UIViewController <FlipsideViewControllerDelegate, MKMapViewDelegate>
{
MKMapView *mapView;
}
#property (nonatomic, retain) IBOutlet MKMapView *mapView;
Rest seems fine.