Sending 'MKPointAnnotation *__strong' to parameter of incompatible type 'id'

Question

I have a MKMapView. In this view I create some annotations. When the user clicks on the annotation disclosure button, I want to push to the detail view.

When I create the annotation, I also fill a NSMutableDictionary to be able to grab the store object afterwards with the point as key.

MKPointAnnotation *point = [[MKPointAnnotation alloc] init];

CLLocationCoordinate2D annotationCoord;
annotationCoord.latitude = [[store storeLatitude] floatValue];
annotationCoord.longitude = [[store storeLongitude] floatValue];

point.coordinate = annotationCoord;

NSString *title = [store storeName];
point.title = title;
point.subtitle = location;

// keep reference to store object with the annotation point as key
[annotationStoreDictionary setObject:store forKey:point];

When the user selects the annotation, I want to call the DetailViewController and pass the object:

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control {

    DetailViewController *con = [storyboard instantiateViewControllerWithIdentifier:@"DetailViewController"];
    Store *store = [annotationStoreDictionary objectForKey:view.annotation];
    con.store = store;

    [[self navigationController] pushViewController:con animated:YES];
}

The problem is that MKPointAnnotation is not compliant with the NSCoping protocol. It says:

Sending 'MKPointAnnotation *__strong' to parameter of incompatible type 'id<NSCoping>'

How can this be fixed?

As @Jesper suggests, subclass MKPointAnnotation and add custom properties to keep a reference to each annotation's Store in the annotation object itself. The separate dictionary is not necessary. Another approach is this: Since you already have a `Store` class, simply make it implement the `MKAnnotation` protocol and add the Store objects themselves to the map. This way, the annotations _are_ the Stores. To create a class that implements MKAnnotation, see http://stackoverflow.com/questions/5939223/store-data-in-mkannotation for one example. — , Oct 28 '14 at 14:03
+1, @Anna . Implementing `MKAnnotation` is a great alternative. — Jesper, Oct 28 '14 at 14:05
@Anna, if you provide this as an answer, I will accept it! Thanks for the input, it worked. — nimrod, Oct 29 '14 at 14:48

score 1 · Answer 1 · answered Oct 28 '14 at 13:37

You can't use something that doesn't conform to the NSCopying protocol as a key in a dictionary. You'll have to use something else that does.

One way of getting around this would be to make a subclass of MKPointAnnotation with extra properties for correlation - and in that case, you may as well also just use the extra property or properties on that object and not go through the dictionary in the first place.

Sending 'MKPointAnnotation *__strong' to parameter of incompatible type 'id'

1 Answers1