Convert MKAnnotation array to set - ios

Question

I have a situation where I have map annotations as [MKAnnotation] array in swift. Now I need to convert this into a set for some operation. How can I do this in swift? Basically I need to add only the non existent annotations on the map while updating the map view.

Answer 1

You can find out if an annotation exists on the map by using mapView.view(for:) as mentioned here:
if (self.mapView.view(for: annotation) != nil) {
print("pin already on mapview")
}

Answer 2

"Basically I need to add only the non existent annotations on the map while updating the map view."
We first need to define what makes two annotations equal (in your scenario). Once that is clear you an override the isEqual method. You can then add annotations to a Set.
Here is an example :
class MyAnnotation : NSObject,MKAnnotation{
var coordinate: CLLocationCoordinate2D
var title: String?
convenience init(coord : CLLocationCoordinate2D, title: String) {
self.init()
self.coordinate = coord
self.title = title
}
private override init() {
self.coordinate = CLLocationCoordinate2D(latitude: 0, longitude: 0)
}
override func isEqual(_ object: Any?) -> Bool {
if let annot = object as? MyAnnotation{
// Add your defintion of equality here. i.e what determines if two Annotations are equal.
return annot.coordinate.latitude == coordinate.latitude && annot.coordinate.longitude == coordinate.longitude && annot.title == title
}
return false
}
}
In the code above two instances of MyAnnotation are considered equal when you they have the same coordinates and the same title.
let ann1 = MyAnnotation(coord: CLLocationCoordinate2D(latitude: 20.0, longitude: 30.0), title: "Annot A")
let ann2 = MyAnnotation(coord: CLLocationCoordinate2D(latitude: 0.0, longitude: 0.0), title: "Annot B")
let ann3 = MyAnnotation(coord: CLLocationCoordinate2D(latitude: 20.0, longitude: 30.0), title: "Annot A")
var annSet = Set<MyAnnotation>()
annSet.insert(ann1)
annSet.insert(ann2)
annSet.insert(ann3)
print(annSet.count) // Output : 2 (ann1 & ann3 are equal)