Trying to use reverseGeocodeLocation, but completionHandler code is not being executing - ios

Question

The issue is that the code inside the completionHandler block is never run; I used breakpoints and the program would skip over the completion handler block in build mode
Below are two functions used within PinALandPlaceMark, where most of my code is located
func generateRandomWorldLatitude()-> Double{
let latitude = Double.random(in: -33 ..< 60)
return latitude
}
func generateRandomWorldLongitude()-> Double{
let longitude = Double.random(in: -180 ..< 180)
return longitude
}
func PinALandPlaceMark() -> MKAnnotation {
var LandBasedCountryHasYetToBeFound : (Bool, CLLocationDegrees?, CLLocationDegrees?)
LandBasedCountryHasYetToBeFound = (false,nil,nil)
let randomPinLocation = MKPointAnnotation()
repeat{
if LandBasedCountryHasYetToBeFound == (false,nil,nil){
let latitude: CLLocationDegrees = generateRandomWorldLatitude()
let longitude: CLLocationDegrees = generateRandomWorldLongitude()
let randomCoordinate = CLLocation(latitude: latitude, longitude: longitude)
let geocoder = CLGeocoder()
geocoder.reverseGeocodeLocation(randomCoordinate, completionHandler: { (placemarks, error) -> Void in
if error != nil{print(error)}else{
guard let placemark = placemarks?.first else{return}
//check which placemark property exists, store in the 0 alpha labelForClosure
if let countryExists = placemark.country {
LandBasedCountryHasYetToBeFound = (true,latitude,longitude)
//country = countryExists as String
// viewController.labelForClosure.text = countryExists
print(" Country Exists!: \(countryExists)")
print(" randomCoordinate \(randomCoordinate)")
}
}
})
}
// print("The country found was on land. This statement is \(LandBasedCountryHasYetToBeFound.occursInCountry)")
else{
let coordinatesOfrandomPinLocation = CLLocationCoordinate2D(latitude: LandBasedCountryHasYetToBeFound.1!, longitude: LandBasedCountryHasYetToBeFound.2!)
randomPinLocation.title = ""//LandBasedCountryHasYetToBeFound.countryName
randomPinLocation.coordinate = coordinatesOfrandomPinLocation
// viewController.mapView.addAnnotation(randomPinLocation)
}
}while LandBasedCountryHasYetToBeFound.0 == false
print("randomPin has been returned, now use pin function inside placemark declaration")
return randomPinLocation
}

Answer 1

Your main problem is that your CLGeocoder instance is held in a local variable inside the loop; This means that it will be released before it has completed its task.
You have a couple of other issues too which would cause you problems even if the reverse geo-coding did complete.
The main one is that you are checking for loop termination using a boolean that is set inside the closure; The closure will execute asynchronously, so the loop will have executed many more times before the boolean is set to true in the case where an address is found.
The second problem is related to and made worse by this; reverse geocoding is rate limited. If you submit too many requests too quickly, Apple's servers will simply return an error. Even if you did wait for the first response before submitting a second, your chances of hitting land at random are pretty low, so you will probably hit this limit pretty quickly.
Ignoring the rate limit problem for the moment, you can use a recursive function that accepts a completion handler rather than using a loop and trying to return a value.
var geoCoder = CLGeocoder()
func pinALandPlaceMark(completion: #escaping (Result<MKAnnotation, Error>) -> Void) {
let latitude: CLLocationDegrees = generateRandomWorldLatitude()
let longitude: CLLocationDegrees = generateRandomWorldLongitude()
let randomCoordinate = CLLocation(latitude: latitude, longitude: longitude)
geocoder.reverseGeocodeLocation(randomCoordinate) { (placemarks, error) in
guard error == nil else {
completion(nil,error)
return error
}
if let placemark = placemarks.first, let _ = placemark.country {
let randomPinLocation = MKPointAnnotation()
randomPinLocation.coordinate = randomCoordinate.coordinate
completionHandler(randomPinLocation,nil)
} else {
pinALandPlaceMark(completion:completion)
}
}
}
The first thing we do is declare a property to hold the CLGeocoder instance so that it isn't released.
Next, this code checks to see if a placemark with a country was returned. If not then the function calls itself, passing the same completion handler, to try again. If an error occurs then the completion handler is called, passing the error
To use it, you would say something like this:
pinALandPlaceMark() { result in
switch result {
case .success(let placemark):
print("Found \(placemark)")
case .failure(let error):
print("An error occurred: \(error)")
}
}