Parsing different queries with one func using SWIFT - json

Question

My problem is - I'm building Weather App that displays 20 different cities at the same time (that's the task). I can do it with one city when i put it in guard let url = URL(string: ) directly like this (London)
struct Constants {
static let API_KEY = "<api-key>"
static let baseURL = "https://api.openweathermap.org/data/2.5/weather?appid=\(API_KEY)&units=metric&q=" // + cityName
}
class APICaller {
static let shared = APICaller()
func getData(completion: #escaping(Result<[WeatherDataModel], Error>) -> Void) {
guard let url = URL(string: "\(Constants.baseURL)London") else { return } // Here is the city i've put
let task = URLSession.shared.dataTask(with: URLRequest(url: url)) { data, _, error in
guard let data = data, error == nil else {
return
}
do {
let results = try JSONDecoder().decode(MainWeatherDataModel.self, from: data)
completion(.success(results.results))
} catch {
completion(.failure(error))
}
}
task.resume()
}
}
My project contains CollectionView inside TableView. Parsed data filling Cells
But it's only one city showing in App. I need 19 more.
So my questions are: How can I implement different queries in URL or Is there a method do to multiple parsing?
Thank you

Answer 1

Here is a very basic example code, to fetch the weather for a number of cities using your modified setup. It shows how to implement different queries using the URL, as per the question.
Note, you should read about (and use) Swift async/await concurrency, to fetch
all the data concurrently.
struct Constants {
static let API_KEY = "api-key"
static let baseURL = "https://api.openweathermap.org/data/2.5/weather?appid=\(API_KEY)&units=metric&q="
}
class APICaller {
static let shared = APICaller()
// -- here
func getData(cityName: String, completion: #escaping(Result<[WeatherDataModel], Error>) -> Void) {
// -- here
guard let url = URL(string: (Constants.baseURL + cityName)) else { return }
URLSession.shared.dataTask(with: URLRequest(url: url)) { data, _, error in
guard let data = data, error == nil else { return }
do {
let results = try JSONDecoder().decode(MainWeatherDataModel.self, from: data)
// -- here
if let weather = results.weather {
completion(.success(weather))
} else {
completion(.success([]))
}
} catch {
completion(.failure(error))
}
}.resume()
}
}
struct ContentView: View {
#State var citiesWeather: [String : [WeatherDataModel]] = [String : [WeatherDataModel]]()
#State var cities = ["London", "Tokyo", "Sydney"]
var body: some View {
List(cities, id: \.self) { city in
VStack {
Text(city).foregroundColor(.blue)
Text(citiesWeather[city]?.first?.description ?? "no data")
}
}
.onAppear {
for city in cities {
fetchWeatherFor(city) // <-- no concurrency, not good
}
}
}
func fetchWeatherFor(_ name: String) {
APICaller.shared.getData(cityName: name) { result in
switch result {
case .success(let arr): citiesWeather[name] = arr
case .failure(let error): print(error) // <-- todo
}
}
}
}
struct WeatherDataModel: Identifiable, Decodable {
public let id: Int
public let main, description, icon: String
}
struct MainWeatherDataModel: Identifiable, Decodable {
let id: Int
let weather: [WeatherDataModel]?
}