[SwiftUI] Weather API 사용하기

 

https://openweathermap.org/api/one-call-3

One Call API 3.0 - OpenWeatherMap

 

- Create a Model Struct

- Decode JSON

 

날씨앱을 만들기 위해서 OpenWeatherMap에서 api를 받아와서 데이터를 얻을 수 있다. 이를 JSON 파일로 바꾸고 이걸 참고해서 Model Struct를 만들면 편하다!

 

 

날씨앱에서 어떤 데이터를 사용할 것인지 확인하고 Model Struct를 만들어주면 된다.

 

예시)

import Foundation
import UIKit

struct Weather: Codable{
    struct Daily: Codable{
        let dt : Date
        struct Temp: Codable{
            let min: Double
            let max: Double
        }
        let temp: Temp
        let humidity: Int
        struct Weather: Codable{
            let id: Int
            let description: String
            let icon: String
            var weatherIconURL: URL{
                let urlString = "http://openweathermap.org/img/wn/\(icon)@2x.png"
                return URL(string: urlString)!
            }
        }
        let weather: [Weather]
        let clouds: Int
        let pop: Double
    }
    let daily: [Daily]
}

 

 

---

 

- Creating an APIService Singleton Class

 

🚨What is the Singleton? 

 

보통 자원을 집약적으로 만드는 것과 객체에 대해 최초 한번 초기화할 때 사용된다 → DB 연결, Login 등

 

import Foundation
import Combine

public class APIService{
    public static let shared = APIService()
    var cancellable = Set<AnyCancellable>()
    public enum APIError: Error{
        case error(_ errorString: String)
    }
    
    public func getJSON<T: Decodable>(urlString: String,
                                      dateDecodingStrategy: JSONDecoder.DateDecodingStrategy = .deferredToDate,
                                      keyDecodingStrategy: JSONDecoder.KeyDecodingStrategy = .useDefaultKeys,
                                      completion: @escaping(Result<T, APIError>) -> Void){
        guard let url = URL(string: urlString) else {completion(.failure(.error(NSLocalizedString("Error: Invalid URL", comment: ""))))
            return
        }
        let request = URLRequest(url: url)
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = dateDecodingStrategy
        decoder.keyDecodingStrategy = keyDecodingStrategy
        URLSession.shared.dataTaskPublisher(for: request)
            .map{ $0.data }
            .decode(type: T.self, decoder: decoder)
            .receive(on: RunLoop.main)
            .sink{(taskCompletion) in
                switch taskCompletion {
                case .finished:
                    return
                case .failure(let decodingError):
                    completion(.failure(APIError.error("Error: \(decodingError.localizedDescription)")))
                }
            } receiveValue: { (decodedData) in
                completion(.success(decodedData))
            }
            .store(in: &cancellable)
    }
}

 

 

---

 

- API에서 데이터 가져와서 출력하기

 

import SwiftUI
import CoreLocation

struct ContentView: View {
    @State private var location: String = ""
    
    var body: some View {
        VStack{
            HStack{
                TextField("Enter location", text: $location)
                Button{
                    getWeatherForecast(for: location)
                }label: {
                    Image(systemName: "circle.fill")
                }
            }
        }
    }
    
    func getWeatherForecast(for location: String){
        let apiService = APIService.shared
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "E, MMM, d"
        CLGeocoder().geocodeAddressString(location){ (placemarks, error) in
            if let error = error {
                print(error.localizedDescription)
            }
            if let lat = placemarks?.first?.location?.coordinate.latitude,
                let lon = placemarks?.first?.location?.coordinate.longitude {
                apiService.getJSON(urlString: "/user's api/",
                                   dateDecodingStrategy: .secondsSince1970) { (result: Result<Weather, APIService.APIError>) in
                    switch result {
                    case .success(let weather):
                        for day in weather.daily{
                            print(dateFormatter.string(from: day.dt))
                            print("   Max: ", day.temp.max)
                            print("   Min: ", day.temp.min)
                            print("   Humidity: ", day.humidity)
                            print("   Description: ", day.weather[0].description)
                            print("   Clouds: ", day.clouds)
                            print("   pop: ", day.pop)
                            print("   IconURL: ", day.weather[0].weatherIconURL)
                        }
                    case .failure(let apiError):
                        switch apiError{
                        case .error(let errorString):
                            print(errorString)
                        }
                    }
                }
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}