title: unrecognized selector sent to instance in swift 4.2
body: <p>I'm stuck with this problem since yesterday and I can't find any solution.</p>
  
  <pre><code>import UIKit
  
  class ViewController: UIViewController {
  
      @IBAction func cameraButton(_ sender: Any) {
  
          cameraResultDisplay.text = "Camera Button Pressed!"
  
      }
  
      @IBOutlet weak var cameraResultDisplay: UILabel!
  
      func processTimer() {
          print("A second has passed!")
      }
  
      override func viewDidLoad() {
          super.viewDidLoad()
          // Do any additional setup after loading the view, typically from a nib.
  
          var timer = Timer()
  
          timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: Selector("processTimer"), userInfo: nil, repeats: true)        
  
      }
  }
  </code></pre>
  
  <p>No matter what I do it still throws this error and this screen is shown out of nowhere:</p>
  
  <pre><code>http://prntscr.com/n1wmcl 
  </code></pre>
  
  <p>And this is the full error log:</p>
  
  <pre><code>2019-03-23 21:42:52.788044+0530 Menu Bars[37292:1510342] -[Menu_Bars.ViewController processTimer]: unrecognized selector sent to instance 0x7fa185607fe0
  2019-03-23 21:42:52.790421+0530 Menu Bars[37292:1510342] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Menu_Bars.ViewController processTimer]: unrecognized selector sent to instance 0x7fa185607fe0'
  *** First throw call stack:
  (
      0   CoreFoundation                      0x000000010ff2f1bb __exceptionPreprocess + 331
      1   libobjc.A.dylib                     0x000000010f4cd735 objc_exception_throw + 48
      2   CoreFoundation                      0x000000010ff4df44 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132
      3   UIKitCore                           0x00000001138a9b4a -[UIResponder doesNotRecognizeSelector:] + 287
      4   CoreFoundation                      0x000000010ff33ed6 ___forwarding___ + 1446
      5   CoreFoundation                      0x000000010ff35da8 _CF_forwarding_prep_0 + 120
      6   Foundation                          0x000000010ef70881 __NSFireTimer + 83
      7   CoreFoundation                      0x000000010fe94f34 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
      8   CoreFoundation                      0x000000010fe94b32 __CFRunLoopDoTimer + 1026
      9   CoreFoundation                      0x000000010fe9439a __CFRunLoopDoTimers + 266
      10  CoreFoundation                      0x000000010fe8ea1c __CFRunLoopRun + 2252
      11  CoreFoundation                      0x000000010fe8de11 CFRunLoopRunSpecific + 625
      12  GraphicsServices                    0x000000011900c1dd GSEventRunModal + 62
      13  UIKitCore                           0x000000011387b81d UIApplicationMain + 140
      14  Menu Bars                           0x000000010eba59d7 main + 71
      15  libdyld.dylib                       0x0000000112388575 start + 1
  )
  libc++abi.dylib: terminating with uncaught exception of type NSException
  (lldb) 
  </code></pre>
  
  <p>I'm following an online course from Udemy and I wrote exactly the same code as the guy in the course writes. I tried a few things but I think I did some stupid things that's why it didn't work. Now I'm stuck with this problem from 2 days and it is giving me headache and there is no one to help me out with this problem. </p>
  
  <p>Please help me with this thanks.</p>