Playground Implementation of Retrofit for swift AKA retroSwift

AppDelegate.swift

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.

        let builder =  RetroSwift.Builder()
            .baseUrl("http://api.openweathermap.org/data/2.5")
            .build()
         _ = RetroSwift(builder: builder)
        return true
 }

ApplicationService.swift

struct ApplicationService {
        
    @GET(path="/weather")
    var getWeather: Weather
    
}

Caller.swift

class ViewController: UIViewController {
    
    let client: ApplicationService = ApplicationService()
    
    ...
    
    func getWeather(city: String) {        
        client.$getWeather(query: ["q": city, "units": "metric"]) { result in
            switch result {
            case .success(let weather):
                print("weather summary in \(city): \(weather.weather.first!.desc), temprature: \(weather.main.temp)°C")
            case .failure(let e):
                print(e.localizedDescription)
            }
        }
    }
}

Models.swift

struct Main: Codable { ... } // left out for brevity

struct WeatherData: Codable { ... }  // left out for brevity

//1. Create one to one mapping to your response JSON
struct Weather: Codable {
    let weather: [WeatherData]
    let main: Main
}