Crash when presenting viewcontroller

0
votes

I am trying to presentViewController but to crashed with following stack trace. Can some one please check and help.

Code to presentViewController

func moveToChatView(){
 SwiftSpinner.show(Strings.loading)

  let destViewController:GroupChatViewController  = UIStoryboard(name:      "GroupChat", bundle:  nil).instantiateViewControllerWithIdentifier("GroupChatViewController") as!    GroupChatViewController
 destViewController.currentRiderRideID = self.riderRideId!
if NSThread.isMainThread() == true{
self.presentViewController(destViewController, animated: true, completion:   nil)
 }else{
    dispatch_sync(dispatch_get_main_queue()){
  self.presentViewController(destViewController, animated: true, completion:   nil)
   }
 }
}

Fatal Exception: NSRangeException 0 CoreFoundation 0x182b482d8 exceptionPreprocess 1 libobjc.A.dylib 0x1948140e4 objc_exception_throw 2 CoreFoundation 0x182a2f4c0 CFStringConvertNSStringEncodingToEncoding 3 UIKit 0x1879e01b4 -[UINib instantiateWithOwner:options:] 4 UIKit 0x1878dc318 -[UIViewController _loadViewFromNibNamed:bundle:] 5 UIKit 0x1875c09bc -[UIViewController loadViewIfRequired] 6 UIKit 0x1875c0928 -[UIViewController view] 7 UIKit 0x187cb618c -[_UIFullscreenPresentationController _setPresentedViewController:] 8 UIKit 0x1878c60dc -[UIPresentationController initWithPresentedViewController:presentingViewController:] 9 UIKit 0x1878e2378 -[UIViewController _presentViewController:withAnimationController:completion:] 10 UIKit 0x1878e48c8 __62-[UIViewController presentViewController:animated:completion:]_block_invoke 11 UIKit 0x1876ae0ec -[UIViewController presentViewController:animated:completion:] 12 Quickride 0x100451968 partial apply for LiveRideMapViewController.(moveToChatView() -> ()).(closure #1) (LiveRideMapViewController.swift:1868) 13 libdispatch.dylib 0x194e91954 _dispatch_client_callout 14 libdispatch.dylib 0x194e9f590 _dispatch_barrier_sync_f_slow_invoke 15 libdispatch.dylib 0x194e91954 _dispatch_client_callout 16 libdispatch.dylib 0x194e9620c _dispatch_main_queue_callback_4CF 17 CoreFoundation 0x182aff7f8 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE 18 CoreFoundation 0x182afd8a0 __CFRunLoopRun 19 CoreFoundation 0x182a292d4 CFRunLoopRunSpecific 20 GraphicsServices 0x18c47f6fc GSEventRunModal 21 UIKit 0x187626f40 UIApplicationMain 22 Quickride 0x100259a70 main (AppDelegate.swift:23) 23 libdyld.dylib 0x194ebea08 start

1
iosswiftuiviewcontroller
Are you sure GroupChatViewController is inside your storyboard GroupChat and not in xib ? – Mohammad Zaid Pathan
Can you drop a breakpoint and tell us which line specifically causes the exception? – Erik
Yeah when trying to present GroupChatViewController I am validating thread is in main thread or not , In this flow it is in background thread so it went to else block and once enter into dispatch_sync(dispatch_get_main_queue()){ self.presentViewController(destViewController, animated: true, completion: nil) } It is crashed, Is it because current view controller is not available – Pra Kash
Which line throws the exception? – markedwardmurray

1 Answers

0
votes

As a rule don't use dispatch_sync , but instead use dispatch_async and you don't have to check if you on the main thread , if it is a UI operation and there is a chance that it will be on a back thread just do dispatch_async to main queue which will perform the UI operation on the next run loop on the main queue and the UI will be 'smooth' ,try this:

func moveToChatView(){
    SwiftSpinner.show(Strings.loading)

    let destViewController:GroupChatViewController  = UIStoryboard(name:"GroupChat", bundle:  nil).instantiateViewControllerWithIdentifier("GroupChatViewController") as!    GroupChatViewController
    destViewController.currentRiderRideID = self.riderRideId!
    dispatch_async(dispatch_get_main_queue()){
       self.presentViewController(destViewController, animated: true,completion:nil)
   }
}