MKAnnotationView not displayed when object creation is performed within a custom annotation class

Question

Environment

Xcode: 5.0.2, Device: iPhone, iOS: iOS 7

I am trying to use the mapView:viewForAnnotation: delegate method. Within this method, if I create the MKAnnotationView object, the pin gets displayed without any issue. Here is the working code:

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation
{
    if ([annotation isKindOfClass:[CustomeAnnotation class]])
    {
        //  CustomeAnnotation *myLocation = (CustomeAnnotation *)annotation;
        MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:@"MyCustomAnnotation"];

        if (annotationView == nil)
        {
            MKAnnotationView *annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"MyCustomAnnotation"];
            annotationView.enabled = YES;
            annotationView.canShowCallout = YES;
            //annotationView.image = [UIImage imageNamed:@"park_icon"];
            annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
        }
        //   annotationView = myLocation.createAnnotationView;
        else
            annotationView.annotation = annotation;

          //return nil;
        return annotationView;

    }
    else
        return nil;
}

When I create a class method and move the MKAnnotationView object creation and property setting within the class method and I call it from the mapView:viewForAnnotation: delegate method, the pin does not appear.

Here is the code for the two methods in question (mapView:viewForAnnotation: and createAnnotationView):

@implementation ViewController

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

    self.mapView.delegate = self;

    CLLocationCoordinate2D baysideParkCoordinates = CLLocationCoordinate2DMake(25.774407, -80.185797);
    CustomeAnnotation *baysideParkAnnotation = [[CustomeAnnotation alloc] initWithTitle:@" Bayfront Park"
                                                                             coordinate:baysideParkCoordinates];
    [self.mapView addAnnotation:baysideParkAnnotation];

}

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation
{
    if ([annotation isKindOfClass:[CustomeAnnotation class]])
    {
        CustomeAnnotation *myLocation = (CustomeAnnotation *)annotation;
        MKAnnotationView *annotationView = [mapView dequeueReusableAnnotationViewWithIdentifier:@"MyCustomAnnotation"];

        if (annotationView == nil)
                annotationView = [myLocation createAnnotationView];
        else
            annotationView.annotation = annotation;

      //  return nil;
        return annotationView;

    }
    else
        return nil;
}

@end

The custom class

#import "CustomeAnnotation.h"

@implementation CustomeAnnotation

-(id)initWithTitle:(NSString *)newTitle coordinate:(CLLocationCoordinate2D) newCoordinate
{
    self = [super init];
    if (self)
    {
        self.title = newTitle;
        self.coordinate = newCoordinate;
    }
    return self;
}


-(MKAnnotationView *)createAnnotationView
{
    MKAnnotationView *annotationView = [[MKAnnotationView alloc] initWithAnnotation:self reuseIdentifier:@"MyCustomAnnotation"];
    annotationView.enabled = YES;
    annotationView.canShowCallout = YES;
    //annotationView.image = [UIImage imageNamed:@"park_icon"];
    annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];

    return annotationView;
}
@end

The import statement for the CustomeAnnotation class is included in the ViewController.h file.

At this point I believe I am not passing back correctly the MKAnnotationView object back to the method call in the ViewController implementation file. Could anyone tell me what is it that I am doing wrong on the second set of code?

Answer 1

In the second set of code, in createAnnotationView, the annotation is not showing because it's not setting the image.

Note that an MKAnnotationView does not have a default image so if you don't set it, the annotation is invisible.

Uncomment the setting of the image (or create an MKPinAnnotationView instead).

The reason the first set of code works (even though it is also creating an MKAnnotationView) is because there's actually a small bug in the code:

MKAnnotationView *annotationView = [mapView dequeue...

if (annotationView == nil)
{
    MKAnnotationView *annotationView = [[MKAnnotationView alloc] init...
    //^^^^^^^^^^^^^^^^ Here, the code declares a NEW, LOCAL variable
    //                 named annotationView but it has no connection to the
    //                 annotationView declared outside the if-block.

Because the annotationView declared outside the if is never set, it stays nil and that's what the delegate method actually returns.

When you return nil from viewForAnnotation, the map view creates a default view for you (a red pin for your annotations, a blue dot for the user location).

To fix the first set of code, don't declare a new, local variable. Just set the variable:

MKAnnotationView *annotationView = [mapView dequeue...

if (annotationView == nil)
{
    annotationView = [[MKAnnotationView alloc] init...

and don't forget to set the image (or create an MKPinAnnotationView instead).