I have now tried lots of things, but none of them seem to work.
I have a for loop which parses some data and converts coordinates into ZIP string:
for i in 0 ... results.count - 1
{
result = results[i]
self.coordinateToString(lat: result.lat, long: result.long, completion: { (place) in
someCell.label.text = place
})
}
func coordinateToString(lat: Double, long: Double, completion: #escaping (String) -> ()) {
let geoCoder = CLGeocoder()
let location = CLLocation(latitude: lat, longitude: long)
var ret = ""
geoCoder.reverseGeocodeLocation(location, completionHandler:
{
placemarks, error -> Void in
guard let placeMark = placemarks?.first else { return }
if let zip = placeMark.postalCode, let town = placeMark.subAdministrativeArea
{
let toAppend = "\(zip)" + " \(town)"
ret = toAppend
}
})
DispatchQueue.main.async {
completion(ret)
}
}
However I never manage to show the correct place in the cell, it always shows empty space because it somehow doesn't wait for the completion handler to finish converting. What am I doing wrong here?
This happens because reverseGeocodeLocation returns right away and its completion handler runs afterwards. This means that ret value may be empty when it gets put on the main queue. You should dispatch to main from within the callback, like so:
func coordinateToString(lat: Double, long: Double, completion: #escaping (String) -> ()) {
let geoCoder = CLGeocoder()
let location = CLLocation(latitude: lat, longitude: long)
var ret = ""
geoCoder.reverseGeocodeLocation(location, completionHandler:
{
placemarks, error -> Void in
guard let placeMark = placemarks?.first else { return }
if let zip = placeMark.postalCode, let town = placeMark.subAdministrativeArea
{
let toAppend = "\(zip)" + " \(town)"
ret = toAppend
DispatchQueue.main.async {
completion(ret)
}
}
})
Of course, given this scenario, you need to handle error cases accordingly. Better yet, use defer, that way completion gets called regardless of what happens:
func coordinateToString(lat: Double, long: Double, completion: #escaping (String) -> ()) {
let geoCoder = CLGeocoder()
let location = CLLocation(latitude: lat, longitude: long)
var ret = ""
geoCoder.reverseGeocodeLocation(location, completionHandler:
{
defer {
DispatchQueue.main.async {
completion(ret)
}
}
placemarks, error -> Void in
guard let placeMark = placemarks?.first else { return }
if let zip = placeMark.postalCode, let town = placeMark.subAdministrativeArea
{
let toAppend = "\(zip)" + " \(town)"
ret = toAppend
}
})
Related
I am having trouble with working over data I receive from server.
Each time server sends data it is new coordinates for each user. I am looping over each incoming data, and I want to send the data in completion to receive them on other end. And update model class with them. At the moment I have two users in server. And sometimes the closure passes data two times, but sometimes just one. And interesting thing is that class properties are not updated, at least I dont see them on UI.
This is function I call when data is received. Response is just string I split to get user data.
func updateUserAdrress(response: String, completion: #escaping (Int, Double, Double, String) -> Void){
var data = response.components(separatedBy: "\n")
data.removeLast()
data.forEach { part in
let components = part.components(separatedBy: ",")
let userID = components[0].components(separatedBy: " ")
let id = Int(userID[1])
let latitude = Double(components[1])!
let longitude = Double(components[2])!
let location = CLLocation(latitude: latitude, longitude: longitude)
let geocoder = CLGeocoder()
geocoder.reverseGeocodeLocation(location) { (placemarks, error) in
if error == nil {
let placemark = placemarks?[0]
if let thoroughfare = placemark?.thoroughfare, let subThoroughfare = placemark?.subThoroughfare {
let collectedAddress = thoroughfare + " " + subThoroughfare
DispatchQueue.main.async {
completion(id!, latitude, longitude, collectedAddress)
}
}
} else {
print("Could not get address \(error!.localizedDescription)")
}
}
}
}
In this function I try to invoke the changes on objects. As the incoming data from server is different the first time I have splited the functionality, so the correct block of code would be called.
func collectUsers(_ response: String){
if users.count != 0{
updateUserAdrress(response: response) { id, latitude, longitude, address in
if let index = self.users.firstIndex(where: { $0.id == id }){
let user = self.users[index]
user.latitude = latitude
user.longitude = longitude
user.address = address
}
}
}else{
var userData = response.components(separatedBy: ";")
userData.removeLast()
let users = userData.compactMap { userString -> User? in
let userProperties = userString.components(separatedBy: ",")
var idPart = userProperties[0].components(separatedBy: " ")
if idPart.count == 2{
idPart.removeFirst()
}
guard userProperties.count == 5 else { return nil }
guard let id = Int(idPart[0]),
let latitude = Double(userProperties[3]),
let longitude = Double(userProperties[4]) else { return nil }
let collectedUser = User(id: id, name: userProperties[1], image: userProperties[2], latitude: latitude, longitude: longitude)
return collectedUser
}
DispatchQueue.main.async {
self.users = users
}
}
}
As I also need user address when app starts in model I have made simular function to call in init so it would get address for user. That seems to be working fine. But for more context I will add the model to.
class User: Identifiable {
var id: Int
let name: String
let image: String
var latitude: Double
var longitude: Double
var address: String = ""
init(id: Int, name: String, image: String, latitude: Double, longitude: Double){
self.id = id
self.name = name
self.image = image
self.latitude = latitude
self.longitude = longitude
getAddress(latitude: latitude, longitude: longitude) { address in
self.address = address
}
}
func getAddress(latitude: Double, longitude: Double, completion: #escaping (String) -> Void){
let location = CLLocation(latitude: latitude, longitude: longitude)
let geocoder = CLGeocoder()
geocoder.reverseGeocodeLocation(location) { (placemarks, error) in
if error == nil {
let placemark = placemarks?[0]
if let thoroughfare = placemark?.thoroughfare, let subThoroughfare = placemark?.subThoroughfare {
let collectedAddress = thoroughfare + " " + subThoroughfare
completion(collectedAddress)
}
} else {
print("Could not get address \(error!.localizedDescription)")
}
}
}
}
And one interesting thing. That when closure receives two times data and I assign them to class, there are no changes on UI.
I made this project on Xcode 13.4.1 because on Xcode 14 there is a bug on MapAnnotations throwing purple warnings on view changes.
i try to get data from parse server. Therefore it takes 2 backgroundthreads. But i dont get it managed to wait for the completion in a right way. So i have splitted it up like following code:
func load(loadCompletion: #escaping () -> ()) {
let delegate = object as! AppDelegate
parseQuery.findObjectsInBackground { (result: [PFObject]?, error: Error?) in
self.getAllData(result: result, delegate: delegate, error: error) {
loadCompletion()
}
}
}
func getAllData(result: [PFObject]?, delegate: AppDelegate, error: Error?, allDataCompletion: #escaping () -> ()) {
if error == nil && result != nil {
for obj in result! {
let date: Date = obj["Date"] as! Date
let coordinates: PFGeoPoint = obj["Coordinates"] as! PFGeoPoint
let imageFile: PFFileObject = obj["Image"] as! PFFileObject
let lat: CLLocationDegrees = coordinates.latitude
let long: CLLocationDegrees = coordinates.longitude
let cllCoordinates = CLLocationCoordinate2D(latitude: lat, longitude: long)
self.getImageData(imageFile: imageFile) { (image) in
let poo = Poo(coordinates: cllCoordinates, dateTime: date, image: image)
delegate.poos.append(poo)
}
}
allDataCompletion()
}
}
func getImageData(imageFile: PFFileObject, imageDataCompletion: #escaping (UIImage?) -> () ) {
var image: UIImage? = nil
imageFile.getDataInBackground { (data, error) in
if error == nil && data != nil {
image = UIImage(data: data!)
}
imageDataCompletion(image)
}
}
So, i want so set up the array in the delegate, but unfortunately the loadCompletion() gets called before the array is filled. Please help me to get this running in right order. Thanks!
A simple solution is to modify your getAllData function and call allDataCompletion after getting image data for the last object.
func getAllData(result: [PFObject]?, delegate: AppDelegate, error: Error?, allDataCompletion: #escaping () -> ()) {
if error == nil && result != nil {
for (idx, obj) in result!.enumerated() {
let date: Date = obj["Date"] as! Date
let coordinates: PFGeoPoint = obj["Coordinates"] as! PFGeoPoint
let imageFile: PFFileObject = obj["Image"] as! PFFileObject
let lat: CLLocationDegrees = coordinates.latitude
let long: CLLocationDegrees = coordinates.longitude
let cllCoordinates = CLLocationCoordinate2D(latitude: lat, longitude: long)
self.getImageData(imageFile: imageFile) { (image) in
let poo = Poo(coordinates: cllCoordinates, dateTime: date, image: image)
delegate.poos.append(poo)
if idx == result!.endIndex-1{
allDataCompletion()
}
}
}
}
}
or Use DispatchGroup / Synchronizing Async Code
I'm trying to to calculate the distance from an event to my current location, sort the results and populate that in a tableview. I keep getting error for optional unwrapped value distance is nil.
private func observeEvents() {
refHandle = ref.observe(.childAdded, with: { (snapshot) -> Void in
let eventDetails = snapshot.value as! Dictionary<String, AnyObject>
let eventID = snapshot.key
let location = eventDetails["location"] as! String!
//calculating distance
self.forwardGeocoding(address: location!)
let distance = self.eventLocation?.distance(from: self.currentLocation!) as Double!
//end calculating
let dateTime = eventDetails["dateTime"] as! String!
let addedByUser = eventDetails["addedByUser"] as! String!
let attending = eventDetails["attendance"] as! String!
if let name = eventDetails["eventName"] as! String! , name.characters.count > 0
{
self.events.append(Events(id:eventID, name: name, location: location!, dateTime: dateTime!, addedByUser: addedByUser!, attending: attending! , distance: distance!))
self.events.sort(by: { $0.distance < $1.distance})
self.tableView.reloadData()
} else {
print("Error ! Can't load events from database")
}
})
} //load events data to uitableview
I created a function to return a CLLocation from an address
func forwardGeocoding(address: String) {
CLGeocoder().geocodeAddressString(address, completionHandler: { (placemarks, error) in
if error != nil {
print(error!)
return
}
if (placemarks?.count)! > 0 {
let placemark = placemarks?[0]
self.eventLocation = placemark?.location
}
})
}
I finally figured out the answer. The issue was the function for distance is called asynchronously there for the result would always be nil. I created a completion handler for the forwardGeocoding function to return latitude and longitude from the address string and call the result inside the nested firebase listener. Here is the code, I hope if someone ran into something similar problem to me will find it helpful.
//Get lat and long
func getCoordinates(address: String, completionHandler: #escaping (_ lat: CLLocationDegrees?, _ long: CLLocationDegrees?, _ error: Error?) -> ()) -> Void {
var _:CLLocationDegrees
var _:CLLocationDegrees
let geocoder = CLGeocoder()
geocoder.geocodeAddressString(address) { (placemarks: [CLPlacemark]!, error: Error!) in
if error != nil {
print("Geocode failed with error: \(error.localizedDescription)")
} else if placemarks.count > 0 {
let placemark = placemarks[0] as CLPlacemark
let location = placemark.location
let lat = location?.coordinate.latitude
let long = location?.coordinate.longitude
completionHandler(lat, long, nil)
}
}
}
Nested call in firebase listener
refHandle = ref.observe(.childAdded, with: { (snapshot) -> Void in
let location = event["address"] as! String
self.getCoordinates(address: location!) { lat, long, error in
if error != nil {
print("Error")
} else {
self.latitude = lat
self.longitude = long
let distance = CLLocation(latitude: self.latitude!,longitude: self.longitude!).distance(from: self.currentLocation!)
if let name = eventDetails["eventName"] as! String! , name.characters.count > 0
{
self.events.append(Events(id:eventID, name: name, location: location!, dateTime: dateTime!, addedByUser: addedByUser!, attending: attending!, distance: distance))
self.events.sort(by: { $0.distance < $1.distance})
self.tableView.reloadData()
} else {
print("Error ! Can't load events from database")
}
}
}
})
Trying to get name of a city, while having latitude and longitude.
Inside a model class Location, I'm using reverseGeocodeLocation(location: , completionHandler: ) func that comes with CLGeocoder (part of CoreLocation).
func getLocationName() {
let geoCoder = CLGeocoder()
let location = CLLocation(latitude: currentLatitude, longitude: currentLongitude)
geoCoder.reverseGeocodeLocation(location, completionHandler: { placemarks, error in
guard let addressDict = placemarks?[0].addressDictionary else {
return
}
if let city = addressDict["City"] as? String {
self.currentCity = city
print(city)
}
if let zip = addressDict["ZIP"] as? String {
print(zip)
}
if let country = addressDict["Country"] as? String {
print(country)
}
})
}
However, in ViewController, after running the getLocationName(), the location.currentCity is nil, since the completion handler is async, and wasn't finished yet.
How can I make sure that the completion handler is finished running so I can access location.currentCity ?
Pass a closure as a function parameter in your getLocationName which
you can call inside the reverseGeocodeLocation closure.
func updateLocation(currentCity : String) -> Void
{
print(currentCity)
}
func getLocationName(callback : #escaping (String) -> Void)
{
let geoCoder = CLGeocoder()
let location = CLLocation(latitude: currentLatitude, longitude: currentLongitude)
geoCoder.reverseGeocodeLocation(location, completionHandler: { placemarks, error in
guard let addressDict = placemarks?[0].addressDictionary else {
return
}
if let city = addressDict["City"] as? String
{
self.currentCity = city
callback(city)
print(city)
}
if let zip = addressDict["ZIP"] as? String {
print(zip)
}
if let country = addressDict["Country"] as? String {
print(country)
}
})
}
In your ViewController...
getLocationName(callback: updateLocation)
I would create a function where location.currentCity is used, and call this function from the completion handler
So if your code looks like:
func foo() {
var location
getLocationName()
print(location.currentcity) // nil
}
change it to:
func foo() {
var location
getLocationName()
}
func bar() {
print(location.currentcity) // someplace
}
and call bar() from your completion handler
When I pass an address string into CLGeocoder.geocodeAddressString(), the function never executes. When debugging, it never enters geocodeAddressString() and instead skips over. location1 does contain a valid address.
func routeToLocation(location1: String, location2: String) {
var location1Parsed = CLLocation()
var location2Parsed = CLLocation()
let geocoder = CLGeocoder()
geocoder.geocodeAddressString(location1, completionHandler: {(placemarks, error) -> Void in
if ((error) != nil) {
print("Error")
}
if let placemark = placemarks?.first{
let coordinates: CLLocationCoordinate2D = placemark.location!.coordinate
location1Parsed = CLLocation(latitude: coordinates.latitude, longitude: coordinates.longitude)
print(location1Parsed.coordinate.latitude)
print(location1Parsed.coordinate.longitude)
}
})
...
}
Does anyone know why this might be happening?
Thanks