Stop dispatch_after

Question

I use an animation for specify a tip to help the interaction with delay using these:

 let delay = 1.8 * Double(NSEC_PER_SEC)
    let time = dispatch_time(DIS         


        

Answer 1

Just sharing, in Swift 4.x, I do this:

var block: DispatchWorkItem?

self.block = DispatchWorkItem { self.go(self) }

// execute task in 2 seconds
DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(3), execute: self.block!)

and then to cancel the block, self.block?.cancel()

Try this sample project:

import UIKit

class ViewController: UIViewController {

    var block: DispatchWorkItem?

    @IBAction func go(_ sender: Any) {
        self.block?.cancel()
        let vc2 = VC2()
        self.navigationController?.pushViewController(vc2, animated: true)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = .white
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        self.block = DispatchWorkItem { self.go(self) }

        // execute task in 2 seconds
        DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(3), execute: self.block!)
    }    
}


class VC2: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = .green
    }
}