how can I use function waiting to get something in swift 3?

Question

I want to use a method that wait for getting some thing and then do some thing else - I have a progressive in my app and want to use a function that waiting for progressive to be 100 percent and then that function execute - in generally I want to know how can I use a method that execute when another things happens - I used group method many times but this is more different(its some thing like listener)

let myGroup = DispatchGroup()

myGroup.enter()
//// Do your task
//// When you task complete
myGroup.leave()
myGroup.notify(queue: DispatchQueue.main) {              
////// do your remaining work         
}

Answer 1

You can use notification, delegate or blocks to do that. Check this answer for delegates. Here is an example for notifications. And this answer contains how to use completion handler blocks They are explained in details here.

I am updating this with delegate example :

//Do this in the class (assuming it as EventViewController) where event occurs


    protocol delegateForEvent {
    func didEventCompleted()
     }

class EventViewController: UIViewController {
var delegate:delegateForEvent!

When the event completed, call this

self.delegate.didEventCompleted()   // call this at the time of color change

And in ViewController or whichever class you want to receive the event (assuming it as ViewController.swift),

In ViewController.swift

class ViewController: UIViewController, delegateForEvent {  // Set delegateForEvent in interface

set the delegate where you create your eventViewController instance in viewController.swift

myEventViewController.delegate = self;   // set it where you created your object

and add the delegate function in viewController.swift

didEventCompleted{
   //here you can do whatever you want to after the event completion
}