Note about MKAnnotation Protocol implementation

Sometimes you just have to take things as they are given, just like that. For example adding MKAnnotation protocol support all you have to do is create an instance variable called "coordinate":

@interface MyPointItem : NSObject <MKAnnotation> {
    NSString *title;
    NSInteger distance;
    CLLocationCoordinate2D coordinate;
}

As Apple documentation says:

"An object that adopts this protocol must implement the coordinate property."

There you are. As long as you remember, WHY you have a variable called "coordinate" INSTEAD OF "location". If you don't remember and apply Natural Naming to your code, your application will start crashing horribly for mysterious reasons...

<Error>: CGImageCreateWithImageProvider: invalid image size: 0 x 0

There seems to be a bug in iOS 4.0 built-in MapKit, which causes error message in both simulator and real device:

<Error>: CGImageCreateWithImageProvider: invalid image size: 0 x 0.

This happens when I open UIViewController, which contains MKMapView (all created with Interface Builder). Since user location is not needed at this moment, I just unchecked "Shows User Location" checkbox on Map View Attributes.

Warning disappears and I'm back on Zero Warning policy!

How to Create Custom Map Annotation Button

Custom accessory button for MKPinAnnotationView right side, create inside MKMapViewDelegate protocol mapView:viewForAnnotation method:

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
[button setImage:[UIImage imageNamed:@"myButton.png"] forState:UIControlStateNormal]; 
view.rightCalloutAccessoryView = button;

Usually sample codes use UIButtonTypeDetailDisclosure as right button, but you can't use that unless you really show additional details. For anything else, you must use a custom button.