NSTimer doesn't find selector [duplicate]

Question

I want to use an NSTimer in a class that doesn't inherit from UIViewVontroller. I have 2 files : a ViewController and a TimerClass like that :

ViewController:

import UIKit

class ViewController: UIViewController {

    var timerClass = TimerClass()

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func viewDidAppear(animated: Bool) {
        timerClass.launchTimer()
    }

}

TimerClass :

import Foundation

class TimerClass {

    var timer = NSTimer()

    init(){}

    func launchTimer(){
        var timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: "timerEnd", userInfo: nil, repeats: true)
    }

    func timerEnd(){
        println("That worked")
    }
}

When I launch that app, I have a crash with :

2015-01-12 19:48:24.322 Timer_TEST[5829:185651] *** NSForwarding: warning: object 0x7fbc3be20710 of class 'Timer_TEST.TimerClass' does not implement methodSignatureForSelector: -- trouble ahead Unrecognized selector -[Timer_TEST.supportFile timerEnd]

Any idea?

Thank you

Answer 1

EDIT: Note that starting in Swift 2.2 you won't be able to make this mistake! You'll use the new #selector syntax (see https://stackoverflow.com/a/35658335/341994), and the compiler won't let you form a selector for a method that isn't exposed to Objective-C.

---

It's merely a question of exposing the Swift function to Objective-C so that it is visible to Objective-C. You have four choices:

• Make TimerClass descend from NSObject (and delete the init implementation):

  class TimerClass : NSObject {
  

• Declare TimerClass with @objc [not in Swift 2.0; use the previous choice instead]:

  @objc TimerClass {
  

• Declare the function with @objc:

  @objc func timerEnd()
  

• Declare the function dynamic (this is probably the worst choice, as it is unnecessary - the function is not dynamic; it does not need to be altered in place by Objective-C, it just needs to be visible):

  dynamic func timerEnd(){