Is there a preset 'index' or something similar that allows me to refer to specific annotations that a user created? Swift 4 - ios

Question

I have an app where the user can search for locations, tap on the row in the table view, and an annotation will be placed at the placemark. I have a button, "meetUpButton" that allows them to put multiple annotations, rather than what my code does by default which is remove the annotation if a new search result is clicked. Is there a way to refer to a specific annotation that my user created, even if they made multiple? For example, say I want to add the latitude of two annotations that my user created...
If I have
let annotation = MKPointAnnotation()
annotation.coordinate.latitude
Is there a way to refer to something like the first annotation with an index of 0 and the next one that my user chose with a 1 or another way? Here's some of my code which might make this clearer.
extension ViewController: handleMapSearch {
func dropPinZoomIn(placemark:MKPlacemark) {
resultSearchController?.isActive = false
// cache the pin
selectedPin = placemark
// clear existing pins
if meetUpOutlet.isEnabled == true {
mapView.removeAnnotations(mapView.annotations)
} else {
}
let annotation = MKPointAnnotation()
annotation.coordinate = placemark.coordinate
annotation.title = placemark.name
if let city = placemark.locality,
let state = placemark.administrativeArea {
annotation.subtitle = "(\(city)) (\(state))"
}
mapView.addAnnotation(annotation)
let span = MKCoordinateSpanMake(0.05, 0.05)
let region = MKCoordinateRegionMake(placemark.coordinate, span)
mapView.setRegion(region, animated: true)
}
}

Answer 1

You can try to use annotations property of MKMapView instance , to get all use
let anns = self.mapView.annotations

Answer 2

You can implement Custom annotation class.
e.g.
class MyAnnotation : NSObject, MKAnnotation {
var coordinate : CLLocationCoordinate2D
var title: String?
var subtitle: String?
var index: Int?
init(location coord:CLLocationCoordinate2D) {
self.coordinate = coord
super.init()
}
}
Usage:
let annotation = MyAnnotation(location: coordinate)
annotation.title = "title"
annotation.subtitle = "subtitle"
annotation.index = 1
Remove annotations (only index == 1)
for annotation in self.mapView.annotations {
guard let annotation = annotation as? MyAnnotation else {
continue
}
if annotation.index == 1 {
self.mapView.removeAnnotation(annotation)
}
}