charvoa

    func fetchMapLessons(_ completionHandler: @escaping ([ObjectModel]?) -> Void) {

        let query = PFQuery(className: "ObjectClass")
            .addAscendingOrder("date")

        query.findObjectsInBackground { (objects, error) in
            guard let obj = objects else {
                completionHandler(nil)
                return
            }

charvoa

    func fetchMapLessons(around: CLLocation,
                         within: Double,
                         _ completionHandler: @escaping ([Any]?) -> Void) {

        let query = PFQuery(className: "ObjectClass")
            .addAscendingOrder("date")
            .whereKey("location",
                      nearGeoPoint: PFGeoPoint(location: around),
                      withinKilometers: within)

charvoa

func mapView(_ mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
    let center = mapView.region.center
    let latitudeDelta = mapView.region.span.latitudeDelta

    let topPin = CLLocation(latitude: center.latitude - (latitudeDelta / 2),
                                longitude: center.longitude)
    let bottomPin = CLLocation(latitude: center.latitude + (latitudeDelta / 2),
                                   longitude: center.longitude)
    let centerLocation = CLLocation(latitude: center.latitude,
                                        longitude: center.longitude)