Inter-thread inter-object communication in Swift 3 with Cocoa - swift

Question

My program consists of three relatively-distinct areas: listening on a network for new state, performing network actions, and updating the UI. So respectively I want three classes: StateListener, ActionSender, and ViewController, each chugging along on separate threads.
Would that it were so simple -- the three need to interact. Some states discovered by the StateListener require Actions to be sent by the ActionSender or the UI to be updated by the ViewController. Some responses to Actions require the UI to be updated by the ViewController. Some UI actions require Actions to be performed by the ActionSender.
Currently I do something like this (pseudocode):
/* ViewController.swift */
class ViewController : blah
{
//...
func buttonPressed()
{
// ?! Need to do an action here but I can't
// because actionSender is initialised below...
}
func viewDidLoad()
{
let actionSender = ActionSender(m_view: self)
let actionQueue = OperationQueue()
let stateListener = StateListener(m_view: self,
m_actionSender: actionSender,
m_actionQueue: actionQueue)
let stateQueue = OperationQueue()
stateQueue.addOperation(stateQueue.listen())
}
}
/* StateListener.swift */
class StateListener
{
// ...
func listen()
{
while true
{
var state = waitForNewState()
if shouldActOn(state)
{
m_actionQueue.addOperation(m_actionSender.act())
}
}
}
}
/* ActionSender.swift */
class ActionSender
{
// ...
func act()
{
var reply = sendAction()
OperationQueue.main.addOperation(m_view.m_textBox.append(reply))
}
}
This is fairly hellish and doesn't even do what I want it to do, because I can't have the ViewController perform actions (ActionSender's require a ViewController reference to update the view after the action, but I tried initialising the ActionSender within ViewController.init and I got bizarre errors to do with a Code.init that I hadn't implemented...). I want to get above ViewController and initialise all these OperationQueues and objects wherever ViewController gets initialised, but I can't find where that is...
What I've done above is basically object-reference injection of each object and OperationQueue. I know there are other ways of doing this (a hierarchy of callbacks, NSNotifications) but I'm unsure of which is best.
My question is in two parts:
What is the best (i.e., fastest, easiest to implement and maintain, most idiomatic in Swift) way to get the inter-object and inter-thread communication I desire?
I currently get things going from ViewController's viewDidLoad function, which seems awful (and means I can't get a 'higher-up' perspective of the ViewController. Where should this stuff go? AppDelegate advertises itself as the 'program startup' area, but I can't access the ViewController from there... XCode seems to have hidden the startup of my app from me!
I really appreciate your responses!

Answer 1

This post greatly helped with question 2 and the problem of passing self as a parameter to a data member in an initialiser : http://blog.scottlogic.com/2014/11/20/swift-initialisation.html
Specifically, I can use this pattern:
class Foo : blah
{
var m_bar : Bar!
init() {
// notice I get away with not initialising m_bar
}
func viewDidLoad {
m_bar = Bar(m_foo: self)
m_bar.doYourThing()
}
}
The blog prefers the following, which I feel I should add here out of gratitude to the author, though I prefer the above.
class Foo : blah
{
lazy var m_bar : Bar = {
return Bar(m_foo: self) // notice I can pass in self
}
init() {
// notice I get away with not initialising m_bar
}
func viewDidLoad {
m_bar.doYourThing()
}
}