how to observe the iOS mapView didChangeVisibleRegion

Question

hello Im working on an app that will show annotations over where the user is currently zoomed into, however I don't know how to use one of the functions because I am fairly new to mapkit.

    func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) {
         if mapView.region.span.latitudeDelta = ?
    }

Im using firebase and don't want to pull out every annotation that has ever been entered but only pull out annotations when a user is at a certain zoom and show those annotations. which is where I'm at a blank, the question mark is where I don't know what to enter. If anyone knows please help!? thank you!

Answer 1

I do not use swift, so I can't provide actual coding.... but the how the coding should work. This can all be performed in an HTTP request thread.

func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) { /* App side */ // HTTP Method here pass the mapView.region.span.latitudeDelta and mapView.region.span.longitudeDelta

/* server side */
// Do math from the delta values passed
// Query the database based off the math
// Output data in json format

/* App side */
// Redraw the map annotations based of the json output

}