MKMapview place pin at location (long/lat)

Question

I have latitude and long values and I need to be able to drop a pin at this location.

Can anybody provide some advice on how to go about this?

Answer 1

This assumes that you have ARC enabled and that you have included the MapKit framework.

First create a class that implements the MKAnnotation protocol. We'll call it MapPinAnnotation.

MapPinAnnotation.h

@interface MapPinAnnotation : NSObject 

@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;
@property (nonatomic, readonly) NSString* title;
@property (nonatomic, readonly) NSString* subtitle;

- (id)initWithCoordinates:(CLLocationCoordinate2D)location
                placeName:(NSString *)placeName
              description:(NSString *)description;

@end

MapPinAnnotation.m

@implementation MapPinAnnotation

@synthesize coordinate;
@synthesize title;
@synthesize subtitle;

- (id)initWithCoordinates:(CLLocationCoordinate2D)location
                placeName:(NSString *)placeName
              description:(NSString *)description;
{
  self = [super init];
  if (self)
  {    
    coordinate = location;
    title = placeName;
    subtitle = description;
  }

  return self;
}

@end

Then add the annotation to the map using the following:

CLLocationCoordinate2D coordinate = CLLocationCoordinate2DMake(34.421496,
                                                              -119.70182);

MapPinAnnotation* pinAnnotation = 
  [[MapPinAnnotation alloc] initWithCoordinates:coordinate
                                      placeName:nil
                                    description:nil];
[mMapView addAnnotation:pinAnnotation];

The containing class will have to implement the MKMapViewDelegate protocol. In particular you will have to define the following function to draw the pin:

- (MKAnnotationView *)mapView:(MKMapView *)mapView 
            viewForAnnotation:(id )annotation
{
  if ([annotation isKindOfClass:[MKUserLocation class]])
  {
    return nil;
  }

  static NSString* myIdentifier = @"myIndentifier";
  MKPinAnnotationView* pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:myIdentifier];

  if (!pinView)
  {
    pinView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:myIdentifier];
    pinView.pinColor = MKPinAnnotationColorRed;
    pinView.animatesDrop = NO;
  }
  return pinView;
}

In this example the MKAnnotation title and subtitle member variables are not used, but they can be displayed in the delegate function.