2.1.4.2 Networking with URLSession (or Alamofire)

Example: Fetching user posts

// Services/ApiService.swift
import Foundation

class ApiService {
    static let shared = ApiService()
    private init() {}

    func fetchPosts(completion: @escaping (Result<[Post], Error>) -> Void) {
        guard let url = URL(string: "http://localhost:4000/api/posts") else { return }

        var request = URLRequest(url: url)
        request.httpMethod = "GET"
        let token = UserDefaults.standard.string(forKey: "authToken") ?? ""
        request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")

        URLSession.shared.dataTask(with: request) { data, response, error in
            if let err = error {
                completion(.failure(err))
                return
            }
            guard let data = data else { return }
            do {
                let posts = try JSONDecoder().decode([Post].self, from: data)
                completion(.success(posts))
            } catch {
                completion(.failure(error))
            }
        }.resume()
    }
}