Convert span value into meters on a mapview

Question

Whenever the user zoom in or out the map i need to know how many meters are currently represented on the map (width or height).

What i need is the inverse function o

Answer 1

Swift 4.2

    func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {

        let mapRect = mapView.visibleMapRect
        let westMapPoint = MKMapPoint(x: mapRect.minX, y: mapRect.midY)
        let eastMapPoint = MKMapPoint(x: mapRect.maxX, y: mapRect.midY)
        let visibleDistance = westMapPoint.distance(to: eastMapPoint)
    }