Return HTTP request data - arrays

Question

I would like to return the var points from my method getAllPoints()
struct tempPoint: Decodable {
let idPoint:Int
let ptName:String
let ptLat:Double
let ptLong:Double
}
func getAllPoints(){
if let url = URL(string: "[MyWebService.com]") {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
let jsonData = Data(jsonString.utf8)
do {
let points = try JSONDecoder().decode([tempPoint].self, from: jsonData)
} catch let error {
print(error)
}
print(jsonString)
}
}
}.resume()
}
}
Results that I got when I do print(points)
[
{"idPoint":6,"ptName":"Maison","ptLat":43.72623997050257,"ptLong":2.202591651830584},
{"idPoint":7,"ptName":"Wheelin","ptLat":42.75754326128173,"ptLong":8.137330631668685},
{"idPoint":8,"ptName":"Animoz","ptLat":45.76321863196126,"ptLong":7.137186047202841},
{"idPoint":9,"ptName":"Hesias","ptLat":45.767222865412144,"ptLong":6.132352002277385},
{"idPoint":10,"ptName":"Marcombes","ptLat":45.76018235160473,"ptLong":4.085466264251463},
{"idPoint":11,"ptName":"Leclan","ptLat":48.80950120948317,"ptLong":2.110623123039061},
{"idPoint":12,"ptName":"Cournon Skatepark","ptLat":39.74138613175866,"ptLong":4.2154977334348906}
]
I wonder if this is possible to return these at the end of my method.
I'm gonna use it in a pickerView and to do a CRUD that's why I would like to store them.
Thank You

Answer 1

use completion closure to "return" your points.
Try something like this:
func getAllPoints(completion: #escaping([tempPoint]) -> ()) { // <-- here
if let url = URL(string: "[MyWebService.com]") {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
do {
let points = try JSONDecoder().decode([tempPoint].self, from: data)
completion(points) // <-- here return the results when done
return
} catch let error {
print(error) // <-- here todo deal with errors
}
}
completion([]) // <-- here todo deal with errors
}.resume()
} else {
completion([]) // <-- here todo deal with errors
}
}
and call the function like this:
getAllPoints() { results in
print("array of points: \(results)")
}

Answer 2

My understanding is that you wanted the api response at the position of calling your function. You can return your response using closures.
The typealias you are seeing in the below code are self defined data types. You can directly add closures in your function but to make it more simple for you I declare those closures with typealias as data types. You can read more about typealias and closures here.
After declaring our own closure types. We need to use them in our function as parameters.
struct TempPoint: Decodable {
let idPoint:Int
let ptName:String
let ptLat:Double
let ptLong:Double
}
typealias ApiResponse = ([TempPoint]) -> Void
typealias ApiError = (Error) -> Void
func getAllPoints(_ completion: #escaping ApiResponse, apiError: #escaping ApiError){
if let url = URL(string: "[MyWebService.com]") {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
let jsonData = Data(jsonString.utf8)
do {
let points = try JSONDecoder().decode([TempPoint].self, from: jsonData)
completion(points)
} catch let error {
print(error)
apiError(error)
}
print(jsonString)
}
}
}.resume()
}
}
Our function after changes would look like above.
Now here is how we can use this function.
override func viewDidLoad() {
super.viewDidLoad()
getAllPoints { [weak self] (points) in
// you update you UI here, be sure to call in main thread when you are doing UI updates in closures.
print(points)
} apiError: { (error) in
print(error)
}
}

Answer 3

It would be efficient if things are loosely coupled which can be done with Delegate pattern.
protocol TempPointDelegate {
func didUpdatePoints(_ tempPoints: [tempPoint])
func didFailWithError(error: Error)
}
and in tempPoint Struct
struct tempPoint: Decodable {
let idPoint:Int
let ptName:String
let ptLat:Double
let ptLong:Double
}
var delegate: TempPointDelegate?
func getAllPoints(){
if let url = URL(string: "[MyWebService.com]") {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
if let jsonString = String(data: data, encoding: .utf8) {
let jsonData = Data(jsonString.utf8)
do {
let points = try JSONDecoder().decode([tempPoint].self, from: jsonData)
self.delegate?.didUpdatePoints(points)
return
} catch let error {
self.delegate?.didFailWithError(error)
return
}
}
}
}.resume()
}
}
finally in your ViewController implement tempPointDelegate delegate
class MainViewController: tempPointDelegate{
override func viewDidLoad() {
super.viewDidLoad()
tempPoint.getAllPoints()
}
func didUpdatePoints(_ tempPoints: [tempPoint]) {
DispatchQueue.main.async {
//process the tempPoints here / call the func to handle tempPoints
}
}
func didFailWithError(error: Error) {
//process the error returned here.
}
}

Answer 4

First of all please name structs with starting uppercase letter (TempPoint).
Second of all the conversion to String and back to Data is pointless
In Swift 5.5 you can use async/await
func getAllPoints() async throws -> [TempPoint] {
guard let url = URL(string: "[MyWebService.com]") else { throw URLError(.badURL) }
let (data, _) = try await URLSession.shared.data(from : url)
return try JSONDecoder().decode([TempPoint].self, from: data)
}
And call it
Task {
do {
let points = try await getAllPoints()
} catch {
print(error)
}
}