http://stackoverflow.com/questions/40145347/how-can-i-remove-the-delay-in-swifts-deinit

deinit.swift

import UIKit
import os.log

// This reported:
//
// 2016-10-19 21:27:58.383124 MyApp[6452:1422313] about to set to `nil`
// 2016-10-19 21:27:58.383439 MyApp[6452:1422313] set to nil
// 2016-10-19 21:27:58.383711 MyApp[6452:1422313] finished setting to `nil`

class ViewController: UIViewController {

    var foo: Foo? = Foo()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
            os_log("about to set to `nil`")
            self.foo = nil
            os_log("finished setting to `nil`")
        }
    }

}

class Foo {
    deinit {
        os_log("set to nil")
    }
}