""" Thread 1: Exception:unrecognized selector sent to instance 0x7fb12cc088c0" """ exception error

Question

I'm learning Xcode with Udacity. I've met problems with exception error. Here's my ViewController.swift doc.

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var recordingLabel: UILabel!
    @IBOutlet weak var recordButton: UIButton!
    @IBOutlet weak var stopRecordingButton: UIButton!
    
    func buttonAction(sender:UIButton){
        
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        stopRecordingButton.isEnabled = false
        
        // Do any additional setup after loading the view.
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        print("viewWillAppear called")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // depose of any resources that can be recreated
    }
    
    @IBAction func recordAudio(_ sender: AnyObject){
            recordingLabel.text = "Recording in Progress"
            stopRecordingButton.isEnabled = true
            recordButton.isEnabled = false
    }
    
    @IBAction func stopRecording(_ sender: AnyObject) {
        recordButton.isEnabled = true
        stopRecordingButton.isEnabled = false
        recordingLabel.text = "Tap to record"
    }

}

and here is my AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {



    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        return true
    }

    // MARK: UISceneSession Lifecycle

    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // Called when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }

    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
        // Called when the user discards a scene session.
        // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
        // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
    }


}

and my error message shows : Thread 1: Exception: "-[SingingScope_Storyboard.ViewController recordButton:]: unrecognized selector sent to instance 0x7fb12cc088c0"

What should I do to debug this? Thank you!

Answer 1

This can happen if you add a selector (a function connected to an event) through the storyboard and then change it in code, resulting in the storyboard being out of sync.

Assuming you're trying to connect buttonAction(sender:UIButton) with your recordButton, try doing this:

1. Mark your function as @IBAction. (maybe you deleted this by mistake after connecting it to the storyboard?) @IBAction func buttonAction(sender: UIButton)
2. Go to the storyboard and delete the existing connection by going to the connections inspector after selecting the button and then deleting any connections (in my screenshot, I would click the x next to View Controller / Your Function):

3. Reconnect the function to the button by dragging the circle next to the event you want to connect to and and dropping over your view controller, and then selecting your buttonAction function.

If this doesn't work try providing some screenshots of your storyboard connections, I'll try to help out more!