NetworkClient.swift

//
//  NetworkClient.swift
//
//  Created by Vidur Murali on 11/12/23.
//

import Foundation

class NetworkClient {
    static func get<T: Decodable>(_ url: URL) async -> T? {
        let urlRequest = URLRequest(url: url)

        var data: Data
        var response: URLResponse
        var result: T?

        do {
            (data, response) = try await URLSession.shared.data(for: urlRequest)

            guard(response as? HTTPURLResponse)?.statusCode == 200 else {
                fatalError("Error Fetching Data")
            }

            do {
                result = try JSONDecoder().decode(T.self, from: data)
            } catch {
                print("Error")
            }
        } catch {
            print("Error")
        }

        return result
    }
    
    static func post<T: Decodable, D: Encodable>(_ url: URL, body: D) async throws -> T? {
        var urlRequest = URLRequest(url: url)
        urlRequest.httpMethod = "POST"
        urlRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")
        
        do {
            let requestBody = try JSONEncoder().encode(body)
            urlRequest.httpBody = requestBody

            let (data, response) = try await URLSession.shared.data(for: urlRequest)

            guard let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
                throw URLError(.badServerResponse)
            }

            let result = try JSONDecoder().decode(T.self, from: data)
            return result

        } catch {
            print("Error: \(error.localizedDescription)")
            throw error
        }
    }
}

USAGE.swift

let url = URL(string: "http://endpoint.com/blah/blah/resource")

// GET
let result: [Todo]? = await NetworkClient.get(url!)

// POST
let todo = Todo("Buy milk")
do {
  let result: Todo? = try await NetworkClient.post(url!, todo)
} catch {
  print("Error")
}