viewForAnnotation throws error when returning nil - objective-c

Question

So I have implemented my viewForAnnotation as such
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation {
static NSString *identifier = #"id";
if ([annotation isKindOfClass:[infl8Node class]]) {
NSLog(#"Creating a pin");
MKPinAnnotationView *annotationView = (MKPinAnnotationView *) [_mapView dequeueReusableAnnotationViewWithIdentifier:identifier];
if (annotationView == nil) {
annotationView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier];
} else {
annotationView.annotation = annotation;
}
annotationView.enabled = YES;
annotationView.canShowCallout = YES;
return annotationView;
}
return nil;
}
However I am still running into this error:
2012-11-18 22:12:35.608 Infl8[5960:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[infl8Node coordinate]: unrecognized selector sent to instance 0x846f460'
Does anyone know what could be causing this error? I have traced it to the case where the annotation is of the class MKUserLocation.
EDIT:
Here is the infl8Node.h file:
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
#import <MapKit/MapKit.h>
#interface infl8Node : NSObject <MKAnnotation>
#property (nonatomic, strong) NSString *accountName;
#property (nonatomic, strong) NSString *status;
#property (nonatomic, strong) CLLocation *location;
#property (nonatomic, strong) NSDictionary *address;
- (id) initWithDictionary:(NSDictionary *)dict;
- (MKMapItem *) mapItem;
#end

Answer 1

A class that implements the MKAnnotation protocol must implement the coordinate property.
The infl8Node class does not appear to do that which is why you are getting that unrecognized selector error.
At a minimum, the class will need to implement a coordinate method which returns the coordinate associated with its location.