Question

Im writing a program in IOS where i mark a few spots on the map with a pin.
Now i have the dequereusableannotationview code that works fine with ONE pin but crashes with i use two pins or try to mark two points on the map.
IT only works when i either comment out ONE annotation or comment out the dequeucode
But the question is….do i even need that dequeue code? as the most pins i will ever have is probably…10..?

Thanks you

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
{
    [super viewDidLoad];

    MKMapView *mv=[[MKMapView alloc]initWithFrame:CGRectZero];
    mv.delegate=self;
    [self setView:mv];

    MapAnnotation* ann=[[MapAnnotation alloc]init];
    CLLocationCoordinate2D location;
    location.latitude=(double)51.501468;
    location.longitude=(double)-0.141596;
    [ann setCoordinate:location];
    [ann setTitle:@"test"];
    [ann setTitle:@"plz work"];
    [mv addAnnotation:ann];
    [ann release];

    MapAnnotation* AnnB=[[MapAnnotation alloc]init];
    CLLocationCoordinate2D locationB;
    locationB.latitude=(double)16.4944;
    locationB.longitude=(double)-151.7364;
    [AnnB setCoordinate:locationB];
    [AnnB setTitle:@"test"];
    [AnnB setSubtitle:@"work"];

    [mv addAnnotation:AnnB];
    [AnnB release];
}

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation{
    MKPinAnnotationView *pinView=nil;

    if (annotation!=mapView.userLocation) {
        static NSString *defaultID=@"MYLoction";

        pinView=(MKPinAnnotationView *)[mapView
                                        dequeueReusableAnnotationViewWithIdentifier:defaultID];
        if (pinView=nil) {
            pinView=[[[MKPinAnnotationView alloc]initWithAnnotation:annotation reuseIdentifier:defaultID]autorelease];

            pinView.pinColor=MKPinAnnotationColorPurple;
            pinView.canShowCallout=YES;
            pinView.animatesDrop=YES;
        }
    }
}

Answer 1

One problem is that when you test for equality in

if (pinView=nil) {

you are using the assignment operator, =, instead of the equality operator, ==. This will cause nil to be assigned to pinView every time, so you will never reuse an annotation. I’m surprised the compiler didn’t catch this.

Also, you aren’t actually returning anything in viewForAnnotation:. Try this instead:

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:
    (id<MKAnnotation>)annotation {
    if(annotation == mapView.userLocation) {
        return nil;
    }

    static NSString *defaultID=@"MYLoction";

    MKPinAnnotationView *pinView = (MKPinAnnotationView *)[mapView 
        dequeueReusableAnnotationViewWithIdentifier:defaultID];

    if (!pinView) {
        pinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation 
            reuseIdentifier:defaultID] autorelease];

        pinView.pinColor=MKPinAnnotationColorPurple;
        pinView.canShowCallout=YES;
        pinView.animatesDrop=YES;
    }

    return pinView;
}