Dispatch Alert Queue for iOS

AlertQueue.swift

//: Playground - noun: a place where people can play

import Foundation
import PlaygroundSupport


class AlertQueue {
  private let queue = DispatchQueue(label: "com.collectivehealth.alertqueue")
  typealias Completion = () -> ()

  func submit(block: @escaping () -> ()) -> Completion {
    let semephore = DispatchSemaphore(value: 0)
    let completion: Completion = {
      semephore.signal()
    }
    queue.async {
      DispatchQueue.main.async {
        block()
      }
      semephore.wait()
    }
    return completion
  }
}


let alertQueue = AlertQueue()

let ftuCompletion = alertQueue.submit {
  print("FTU running on the main thread")
  sleep(1)
}

let loginAlert = alertQueue.submit {
  print("Presenting the login alert")
  sleep(1)
}

let someOtherAlert = alertQueue.submit {
  print("Presenting still another alert")
  sleep(1)
}

//ftuCompletion()
//loginAlert()
//someOtherAlert()

PlaygroundPage.current.needsIndefiniteExecution = true