Using PromiseKit and AwaitKit to write synchronous looking async code.

SwiftAsyncAwaitExample.swift

import PromiseKit
import AwaitKit

struct Todo: Decodable {
  var userId: Int
  var id: Int
  var title: String
  var completed: Bool
}

function loadTodos() -> Promise<[Todo]> {
  return async {
    // get promises for each HTTP request
    let requestPromises = Array(0...10).compactMap { (todo) -> Promise<(data: Data, response: URLResponse)>? in
      let urlString = "https://jsonplaceholder.typicode.com/todos/\(todo)"
      guard let url = URL(string: urlString) else { return }
      return URLSession.shared.dataTask(.promise, with: url).validate()
    }

    // wait for all the promises to complete and iterate through the responses
    let results = try await(when(fulfilled: requestPromises))
    
    // decode the JSON from the responses as Todo objects
    return results.map { try JSONDecoder().decode(Todo.self, from: $0.data) }
  }
}

function printTodos() {
  firstly {
    loadTodos()
  }.done { todos in
    todos.forEach { print($0) }
  }.catch { error in
    print("Handle me!!")
  }
}