How to find the user's location in swift? - swift

Question

Hello I am developing an application for ios and one of it's functions has to find the user's current location. Here is my code:
import UIKit
import MapKit
import CoreLocation
import SwiftyJSON
struct City {
let name : String
let location : CLLocation
let description :String
let imageName : String
func distanceTo(location:CLLocation) -> Int
{
let distanceMeters = location.distanceFromLocation(self.location)
let distanceKilometers = distanceMeters / 1000.00
return Int(round(100 * distanceKilometers) / 100)
}
}
class FirstViewController: UIViewController, CLLocationManagerDelegate {
#IBOutlet weak var LabelTest: UILabel!
#IBOutlet weak var Slider: UISlider!
#IBOutlet weak var LabelValueSlider: UILabel!
var MySliderCurrentValue = Double()
var manager = CLLocationManager()
var userLoc: CLLocationCoordinate2D!
{
willSet{
self.orderCitysByProximity()
self.filterCitysByProximity(Int(self.Slider.value))
self.LocateMe(manager)
}
}
var cities = [City]()
var nearbyCities = [City]()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let path: String = NSBundle.mainBundle().pathForResource("cities", ofType: "json") as String!
let jsonData = NSData(contentsOfFile: path) as NSData!
//let ReadableJSON = JSON ( data:jsonData, options: NSJSONReadingOptions.MutableContainers, error: nil )
do {
let jsonObject = try NSJSONSerialization.JSONObjectWithData(jsonData!, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]
for city in jsonObject["cities"] as! [[String:AnyObject]] {
//let coordinates = position["Position"] as! [String:CLLocationDegrees]
let cityName = city["Name"] as! String
let latitude = city["Latitude"] as! Double
let longitude = city["Longitude"] as! Double
let description = city["Description"] as! String
let image = city["Image"] as! String
let location = CLLocation(latitude: latitude, longitude: longitude)
let city = City(name: cityName, location: location,description: description, imageName: image)
cities.append(city)
// print(cities)
}
self.orderCitysByProximity()
self.filterCitysByProximity(Int(self.Slider.value))
} catch let error as NSError {
print(error)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func SliderChange(sender: UISlider) {
let MySliderCurrentValue: String = String(Int(sender.value))
LabelValueSlider.text = MySliderCurrentValue
self.filterCitysByProximity(Int(sender.value))
}
#IBAction func goToTableView()
{
if let tableViewController = self.storyboard?.instantiateViewControllerWithIdentifier("tableViewController") as? TableViewController
{
tableViewController.cities = self.nearbyCities
self.navigationController?.pushViewController(tableViewController, animated: true)
}
}
func filterCitysByProximity(kilometers:Int)
{
self.nearbyCities.removeAll()
for city in self.cities {
if(city.distanceTo(self.userLoc) <= kilometers*2)
{
self.nearbyCities.append(city)
}
}
self.LabelTest.text = "you have \(self.nearbyCities.count) cities nearby"
let OrderedArray = self.nearbyCities.sort({ $0.distanceTo(self.userLoc) < $1.distanceTo(self.userLoc) })
self.nearbyCities = OrderedArray
}
func orderCitysByProximity()
{
let OrderedArray = self.cities.sort({ $0.distanceTo(self.userLoc) < $1.distanceTo(self.userLoc) })
self.cities = OrderedArray
}
#IBAction func LocateMe(sender: AnyObject) {
manager.delegate = self
manager.desiredAccuracy = kCLLocationAccuracyBest
manager.requestWhenInUseAuthorization()
manager.startUpdatingLocation()
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let userlocation: CLLocation = locations[0] as CLLocation
manager.stopUpdatingLocation()
let location = CLLocationCoordinate2D(latitude: userlocation.coordinate.latitude, longitude: userlocation.coordinate.longitude)
self.userLoc = location
}
}
On the bottom you will see the func locationManager, where I am trying to find the user's current location. Would you please advise me how to start this function so that the app recognise when I type userLoc. userLoc are the coordinations of the user and I have to use them in other functions like func filterCitysByProximity, and the rest, which you can see in the code.

Answer 1

Reason of your problem :-
When you call the delegate of the CLLocationManager in viewDidLoad() it takes some time to retrieve the usersCurrent Location , but even before usersLocation could relay back to you, your functions requiring usersCurrent Location were being triggered as you had called them in viewDidLoad() thus causing the error!
your Code should look like this:-
import UIKit
import MapKit
import CoreLocation
import SwiftyJSON
struct City {
let name : String
let location : CLLocation
let description :String
let imageName : String
func distanceTo(location:CLLocation) -> Int
{
let distanceMeters = location.distanceFromLocation(self.location)
let distanceKilometers = distanceMeters / 1000.00
return Int(round(100 * distanceKilometers) / 100)
}
}
class FirstViewController: UIViewController, CLLocationManagerDelegate {
#IBOutlet weak var LabelTest: UILabel!
#IBOutlet weak var Slider: UISlider!
#IBOutlet weak var LabelValueSlider: UILabel!
var MySliderCurrentValue = Double()
var locationManager = CLLocationManager()
var userLoc : CLLocation!
var cities = [City]()
var nearbyCities = [City]()
override func viewDidLoad() {
super.viewDidLoad()
let path: String = NSBundle.mainBundle().pathForResource("cities", ofType: "json") as String!
let jsonData = NSData(contentsOfFile: path) as NSData!
do {
let jsonObject = try NSJSONSerialization.JSONObjectWithData(jsonData!, options: NSJSONReadingOptions.MutableContainers) as! [String:AnyObject]
for city in jsonObject["cities"] as! [[String:AnyObject]] {
//let coordinates = position["Position"] as! [String:CLLocationDegrees]
let cityName = city["Name"] as! String
let latitude = city["Latitude"] as! Double
let longitude = city["Longitude"] as! Double
let description = city["Description"] as! String
let image = city["Image"] as! String
let location = CLLocation(latitude: latitude, longitude: longitude)
let city = City(name: cityName, location: location,description: description, imageName: image)
cities.append(city)
}
} catch let error as NSError {
print(error)
}
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.distanceFilter = kCLDistanceFilterNone
locationManager.requestWhenInUseAuthorization()
locationManager.startMonitoringSignificantLocationChanges()
locationManager.startUpdatingLocation()
if locationManager.respondsToSelector(#selector(locationManager.requestWhenInUseAuthorization)) {
locationManager.requestWhenInUseAuthorization()
locationManager.requestLocation()
}
else {
locationManager.startUpdatingLocation()
}
}
#IBAction func SliderChange(sender: UISlider) {
let MySliderCurrentValue: String = String(Int(sender.value))
LabelValueSlider.text = MySliderCurrentValue
if userLoc != nil{
self.filterCitysByProximity(Int(sender.value), location: userLoc)
}else{
let alertC : UIAlertController = UIAlertController(title: "Iwin", message: "UserLocation Not Updated wait a while", preferredStyle: .Alert)
let okAction : UIAlertAction = UIAlertAction(title: "oK", style: .Default, handler: { (okActn) in
print("User pressed ok")
})
alertC.addAction(okAction)
alertC.popoverPresentationController?.sourceView = view
alertC.popoverPresentationController?.sourceRect = view.frame
self.presentViewController(alertC, animated: true, completion: nil)
}
}
//Segue to .. :-
#IBAction func goToTableView()
{
if let tableViewController = self.storyboard?.instantiateViewControllerWithIdentifier("tableViewController") as? TableViewController
{
tableViewController.cities = self.nearbyCities
print(nearbyCities)
self.navigationController?.pushViewController(tableViewController, animated: true)
}
}
#IBAction func LocateMe(sender: AnyObject) {
}
//Class Functions call :-
func filterCitysByProximity(kilometers:Int, location: CLLocation)
{
self.nearbyCities.removeAll()
for city in self.cities {
if(city.distanceTo(location) <= kilometers*2)
{
self.nearbyCities.append(city)
}
}
self.LabelTest.text = "you have \(self.nearbyCities.count) cities nearby"
let OrderedArray = self.nearbyCities.sort({ $0.distanceTo(location) < $1.distanceTo(location) })
self.nearbyCities = OrderedArray
}
func orderCitysByProximity(location: CLLocation)
{
let OrderedArray = self.cities.sort({ $0.distanceTo(location) < $1.distanceTo(location) })
self.cities = OrderedArray
}
//Location Manager Functions :-
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
userLoc = locations[0] as CLLocation
locationManager.stopUpdatingLocation()
print(userLoc)
self.orderCitysByProximity(userLoc)
self.filterCitysByProximity(Int(self.Slider.value), location : userLoc)
}
func locationManager(manager: CLLocationManager, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
if status == .AuthorizedWhenInUse {
print("authorised call came . . . . ")
locationManager.startUpdatingLocation()
}
}
func locationManager(manager: CLLocationManager, didFailWithError error: NSError){
print(error.localizedDescription)
locationManager.stopUpdatingLocation()
}
}
Add privacy - location usage description : Result to your info.plist
Also if your didUpdateLocations function doesn't get called
reset your location Services by going into settings->General->Reset
Try google, you will find multiple questions