Zoom on multiple locations using 'MKMapView' - ios

Question

I am using the code below to retrieve data from MySQL to show multiple locations on MKMapView using Swift.
The data and locations shows on the map, but what I could not figure out is how to adjust the zoom to cover all locations in that area.
func parseJSON(_ data:Data) {
var jsonResult = NSArray()
do {
jsonResult = try JSONSerialization.jsonObject(with: data, options:JSONSerialization.ReadingOptions.allowFragments) as! NSArray
} catch let error as NSError {
print(error)
}
var jsonElement = NSDictionary()
let locations = NSMutableArray()
for i in 0 ..< jsonResult.count
{
jsonElement = jsonResult[i] as! NSDictionary
let location = LocationModel()
//the following insures none of the JsonElement values are nil through optional binding
if let evIdL = jsonElement["id"] as? String,
let evUserNameL = jsonElement["username"] as? String,
let evNotikindL = jsonElement["notikind"] as? String,
let evLatiL = jsonElement["lati"] as? String,
let evLongiL = jsonElement["longi"] as? String,
let evLocatL = jsonElement["locat"] as? String,
let evTimedateL = jsonElement["timedate"] as? String,
let evDistanceL = jsonElement["distance"] as? String
{
location.evId = evIdL
location.evUsername = evUserNameL
location.evNotikind = evNotikindL
location.evLati = evLatiL
location.evLongi = evLongiL
location.evLocat = evDistanceL
location.evTimedate = evTimedateL
location.evDisatnce = evDistanceL
location.evLocat = evLocatL
// the code to show locations
let latiCon = (location.evLati as NSString).doubleValue
let longiCon = (location.evLongi as NSString).doubleValue
let annotations = locations.map { location -> MKAnnotation in
let annotation = MKPointAnnotation()
annotation.title = evNotikindL
annotation.coordinate = CLLocationCoordinate2D(latitude:latiCon, longitude: longiCon)
return annotation
}
self.map.showAnnotations(annotations, animated: true)
self.map.addAnnotations(annotations)
}
locations.add(location)
}
DispatchQueue.main.async(execute: { () -> Void in
self.itemsDownloaded(items: locations)
})
}
I am using PHP file to connect with MySQL, as I said the code working and showing the locations but the zoom focus on one location only.

Answer 1

You can try
DispatchQueue.main.async {
self.map.addAnnotations(annotations)
self.map.showAnnotations(annotations, animated: true)
// make sure itemsDownloaded needs main ??
self.itemsDownloaded(items: locations)
}