ClojureAgentInSwift.swift

gistfile1.txt

import Foundation

/*
Same API as Clojure's agents, but sadly not based on a lockless compare-and-swap operation since Swift doesn not provide one yet.


*/

class Agent<T>
{
  private let q = DispatchQueue.init(label:"readwrite")
  private let computeQ = DispatchQueue.init(label: "compute")
  private var value:T

  init(initial:T) {
    self.value = initial
  }

  /// asynchronously update the value
  func send(f:@escaping ((T)->T)) -> Void
  {
    self.computeQ.async {
      let oldval = self.read()
      let newval = f(oldval)

      self.q.async {
        self.value = newval
      }
    }
  }

  func read() -> T
  {
    return self.q.sync(execute: { () -> T in
      return self.value
    })
  }

  func await() {
    self.q.sync(execute: {})
  }
}