Calling function from another ViewController in swift

Question

I have already looked in Stackoverflow but I can't get an answer. I want to create function that stop playing the sound in another ViewController. But when I clicked the stop button, it cracked and showed "EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)". This is my code.

First ViewController

import UIKit
import AVFoundation

class FirstVC: UIViewController {

   var metronome: AVAudioPlayer!
   override func viewDidLoad() {
       super.viewDidLoad()
   do {
        let resourcePath1 = Bundle.main.path(forResource: "music", ofType: "mp3")
        let url = NSURL(fileURLWithPath: resourcePath1!)
        try metronome = AVAudioPlayer(contentsOf: url as URL)

        metronome.prepareToPlay()
        metronome.play()
    } catch let err as NSError {
        print(err.debugDescription)
    }
}

and another Viewcontroller is

import UIKit
class SecondVC: UIViewController {
   var metronomePlay = FirstVC()

@IBAction func stopBtnPressed(_ sender: Any) {
   metronomePlay.metronome.stop() //"EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)"
   }
}

You can use Notification center by sending notification to second view controller. I think this will helpful to you — Ronak Adeshara, Feb 09 '17 at 11:41

shanezzar · Answer 1 · 2023-03-20T19:06:43.560

As of Swift 5+:

Put this in sending controller:

NotificationCenter.default.post(name: Notification.Name(rawValue: "disconnectPaxiSockets"), object: nil)

Put this in receiving controller viewDidLoad() or viewWillAppear():

NotificationCenter.default.addObserver(self, selector: #selector(disconnectPaxiSocket(_:)), name: Notification.Name(rawValue: "disconnectPaxiSockets"), object: nil)

and then the following function in your receiving controller class:

@objc func disconnectPaxiSocket(_ notification: Notification) {
    ridesTimer.invalidate()
    shared.disconnectSockets(socket: self.socket)
}

score 25 · Answer 2 · answered Sep 11 '19 at 14:19

Swift 5:

Put this in the Action

NotificationCenter.default.post(name: Notification.Name("NewFunctionName"), object: nil)

Put this in viewdidload() in a different viewcontroller (where is the function you want to use)

NotificationCenter.default.addObserver(self, selector: #selector(functionName), name: Notification.Name("NewFunctionName"), object: nil)

The function

 @objc func functionName (notification: NSNotification){ //add stuff here}

I hope I was helpful

score 21 · Answer 3 · answered Feb 09 '17 at 11:32

You are creating a NEW copy of FirstVC and calling stop on something that is not yet initialised.

You should really use a delegate in this case, something like

protocol controlsAudio {
   func startAudio()
   func stopAudio()
}

class FirstVC: UIViewController, controlsAudio {
    func startAudio() {}
    func stopAudio() {}

    // later in the code when you present SecondVC
    func displaySecondVC() {
       let vc = SecondVC()
       vc.delegate = self
       self.present(vc, animated: true)
    }

}

class SecondVC: UIViewController {
    var delegate: controlsAudio?

    // to start audio call self.delegate?.startAudio)
    // to stop audio call self.delegate?.stopAudio)

}

So you are passing first VC to the second VC, so when you call these functions you are doing it on the actual FirstVC that is in use, rather than creating a new one.

You could do this without protocols if you like by replacing the var delegate: controlsAudio? with var firstVC: FirstVC? and assigning that, but I wouldn't recommend it

didn't work for me with protocol because delegate in SecondVC comes nil — Marcel, Jan 27 '21 at 22:07
it looks like it worked for the 19 people that upvoted the answer. are you using weak references? are you setting the delegate properly and holding a reference to the VC? — Scriptable, Jan 28 '21 at 15:46
@Marcel, I met the same issue. I don't use storyboard, so need to declare `self.delegate = FirstVC()` in SecondVC explicitly, and mostly in `viewDidLoad` method. That fix my issue, otherwise you would get nil as the delegate property is never assigned a value. — Zhou Haibo, Jan 29 '21 at 10:48

score 13 · Answer 4 · answered Jun 19 '18 at 21:44

13

I use this way to call my functions from another viewControllers:

let sendValue = SecondViewController();
sendValue.YourFuncion(data: yourdata);

answered Jun 19 '18 at 21:44

Minas Petterson

1,159
1
8
6

this workd fine but it have to be wrapped in ```DispatchQueue.main.async { // UI work here }``` – Lukáš Šálek Dec 05 '22 at 10:25

Amyth · Answer 5 · 2019-09-12T14:56:56.000

You can call function from other viewControllers in many ways.

Two ways that are already discussed above are by delegates & protocols and by sending notifications.

Another way is by passing closures to your second viewController from firstVC.

Below is the code in which while segueing to SecondVC we pass a closure to stop the metronome. There will be no issue because you are passing the same firstVC (not creating a new instance), so the metronome will not be nil.

class FirstVC: UIViewController {

   var metronome: AVAudioPlayer!
   override func viewDidLoad() {
      super.viewDidLoad()
      do {
           let resourcePath1 = Bundle.main.path(forResource: "music", ofType: "mp3")
           let url = NSURL(fileURLWithPath: resourcePath1!)
           try metronome = AVAudioPlayer(contentsOf: url as URL)

           metronome.prepareToPlay()
           metronome.play()
        } catch let err as NSError {
            print(err.debugDescription)
        }

      let secondVC = SecondVC()
      secondVC.stopMetronome = { [weak self] in
        self?.metronome.stop()
      }
      present(secondVC, animated: true)

    }
}


class SecondVC: UIViewController {
   var metronomePlay = FirstVC()
   var stopMetronome: (() -> Void)? // stopMetronome closure

   @IBAction func stopBtnPressed(_ sender: Any) {
      if let stopMetronome = stopMetronome {
         stopMetronome() // calling the closure
      }

   }

 }

Man, you've saved me from many spared efforts! Thanks a ton! — K307, Aug 02 '20 at 08:37

score 3 · Answer 6 · answered Feb 09 '17 at 11:31

3

var metronomePlay = FirstVC()

you are creating a new instance on FirstVC, instead you should perform the function on the same instance that of already loaded FirstVC.

answered Feb 09 '17 at 11:31

Emel Elias

572
7
18

score 3 · Answer 7 · edited Mar 19 '18 at 04:10

Updating @Scriptable's answer for Swift 4

Step 1 :

Add this code in your view controller, from which you want to press button click to stop sound.

@IBAction func btnStopSound(_ sender: AnyObject)
{
    notificationCenter.post(name: Notification.Name("stopSoundNotification"), object: nil)

}

Step 2:

Now its final step. Now add this below code, to your result view controller, where you want to automatically stop sound.

func functionName (notification: NSNotification) {
           metronomePlay.metronome.stop()
}

override func viewWillAppear(animated: Bool) {
           NSNotificationCenter.defaultCenter().addObserver(self, selector: "functionName",name:"stopSoundNotification", object: nil)

}

Note: This is not technically my answer converted to Swift 4. My answer uses the delegate pattern which is used in all Swift versions. This is just a different way of doing it in Swift 4. — Scriptable, Apr 12 '18 at 07:40

score 0 · Answer 8 · answered Feb 09 '17 at 11:30

You are initialising metronome in viewDidLoad method of FirstVC. In SecondVC, you are initialising metronomePlay as a stored property, but never asking for ViewController's view and thus viewDidLoad of FirstVC is not getting called which results in metronome(stored property) not getting initialised.

bartlomiej.n · Answer 9 · 2018-04-15T17:16:46.383

0

You initialize metronome on FirstVC in viewDidLoad, which won't happen until you load the view of metronomePlay instantiated in SecondVC.

You have to call _ = metronomePlay.view, which will lazily load the view of SecondVC and subsequently execute viewDidLoad, before actually calling metronomePlay.metronome.

edited Apr 15 '18 at 17:16

answered Feb 09 '17 at 12:17

bartlomiej.n

500
6
19

score -1 · Answer 10 · answered Feb 09 '17 at 11:44

-1

Try this in SecondVC. var metronomePlay = FirstVC().metronome

answered Feb 09 '17 at 11:44

guestme

1

1

that would be accessing a new instance, not the current instance that is currently playing. – Scriptable Feb 09 '17 at 11:45

score -1 · Answer 11 · answered Mar 19 '18 at 07:02

-1

Either use the notification process to stop from anywhere or use same FirstVC instance from SecondVC class.

answered Mar 19 '18 at 07:02

Zoeb S

695
1
7
21

Could you please share some snippet of the process you're stating? – Arjun Aug 07 '19 at 05:13

Calling function from another ViewController in swift

11 Answers11

Linked