Cannot Assign the variables of a function to the Labels on Swift - swift

Question

I am working on an app that Decode a JSON file and creates three variables out of the function: Status,emptySlots,freeBikes. I want to assign these values to labels. However, no matter what I do, I was unable to get any output with any method.
The function code:
func getBikeData(stationName:String){
if let url = URL(string: "https://api.citybik.es//v2/networks/baksi-bisim"){
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard let dataResponse = data, error == nil else {
print(error?.localizedDescription ?? "Response Error")
return
}
do {
//here dataResponse received from a network request
let jsonResponse = try JSONSerialization.jsonObject(with:
dataResponse, options: [])
print(jsonResponse) //Response result
do {
//here dataResponse received from a network request
let decoder = JSONDecoder()
//Decode JSON Response Data
let model = try decoder.decode(ResponseJSON.self, from: dataResponse)
print(model)//Output - 1221
if let station = model.network.stations.first(where: { $0.name == stationName }) {
//get the properties of station here as per requirement
let emptySlots: Int = station.empty_slots
let freeBikes: Int = station.free_bikes
let Status: String = station.extra.status
print(emptySlots, freeBikes, Status)
}
}
catch let parsingError {
print("Error", parsingError)
}
} catch let parsingError {
print("Error", parsingError)
}
}
task.resume()
}
}
Any help is gladly appreciated. I have already tried to return the variables, and using completion block.
ResponseJSON Struct:
struct ResponseJSON: Codable {
let network: Stations
}

Answer 1

One way to solve this is to use a closure. To simplify things create a struct that holds the values
struct BikeResponse {
let status: String
let freeBikes: Int
let emptySlots: Int
}
And then modify your function declaration to
func getBikeData(stationName:String, completion: (BikeResponse)->(Void)){
and then after the decoding you call the completion handler
if let station = model.network.stations.first(where: { $0.name == stationName }) {
let response = BikeResponse(status: station.extra.status,
freeBikes: station.free_bikes,
emptySlots: station.empty_slots)
completion(response)
And then in your completion code you can assign the values to your labels
getBikeData(stationName: "ABC") { response in
DispatchQueue.main.async {
someLabel.text = response.status
//...
}
}

Answer 2

Simplest solution:
if let station = model.network.stations.first(where: { $0.name == stationName }) {
DispatchQueue.main.async {
self.emptySlotsLabel.text = String(station.empty_slots)
self.freeBikesLabel.text = String(station.free_bikes)
self.statusLabel.text = station.extra.status
}
}
emptySlotsLabel, freeBikesLabel and statusLabel are the labels, change the names to the real names

Answer 3

you need to add completion handler to you function. Because you are trying to make async query.
After calling getbikedata func you can assign value to your labels.
Sample code looks like this:
func getBikeData(stationName:String, completion: #escaping (Station) -> Void) {
// ... your code here
if let station = model.network?.stations?.first(where: { $0.name == stationName }) {
//get the properties of station here as per requirement
// let emptySlots: Int = station.emptySlots!
// let freeBikes: Int = station.freeBikes!
// let Status: String = (station.extra?.status)!.rawValue
completion(station)
}
// ... other your code here
}
And usage:
getBikeData(stationName: stationName) { (station) in
print(station)
// For example
label.text = station.emptySlots
}