Unable to trigger Segue to manually load VC - self.navigationController is Nil? - ios

Question

EDIT
After some more digging around it has become apparent that if i try to call a segue from the view controller class after a fast application switch to/from Safari i get an exception stating that the segue does not exist. It definitely does, in the VC that is loaded on screen, and i have checked the spelling and it's 100% correct.
What makes it even weirder is that if i call that exact same method from an IBAction it works fine.
Here's the code i am using:
-(void)goToPhotoPage{
[self performSegueWithIdentifier:#"twitterAuthComplete" sender:self];
}
If i call this when the app resumes i get an exception, however if i call it from this IBAction, attached to a UIButton, with doing nothing different the segue works as expected and no exception.
- (IBAction)twitterToPhoto:(id)sender
{
[self goToPhotoPage];
}
Arrrrgrghrhhgrgrg!
ORIGINAL QUESTION
I am working on an iPad application that uploads user photos to Facebook/Twitter.
As part of the process i have to jump to Safari to do OAuth for twitter, the app then jumps back via a specific URL and get's the tokens e.t.c
However for some reason when the application re-awakes i cannot trigger any segue's or manually load any VC's.
I have a success block in my AppDelegae which get's called when the upload is complete which calls a method in the VC to close a spinner and segue to the success view.
The spinner stops as expected, but no matter what i try i cannot get the segue to work.
Everything is hooked up, the segue has an ID and i get no error or exceptions in the console, just nothing happens. The only way i can get code triggered segue to work after this point is to use a user trigger one connect to a UIButton, after that one complete they start to work again.
Here is the code with callback in my AppDelegate:
- (void)postToTwitter:(NSString*)postText image:(UIImage*)image
{
NSData *data = UIImageJPEGRepresentation(image, 0.5);
[_twitter postStatusUpdate:postText
mediaDataArray:#[data]
possiblySensitive:nil
inReplyToStatusID:nil
latitude:nil
longitude:nil
placeID:nil
displayCoordinates:nil
uploadProgressBlock:^(NSInteger bytesWritten, NSInteger totalBytesWritten, NSInteger totalBytesExpectedToWrite) {
} successBlock:^(NSDictionary *status) {
ViewController * vc = [[ViewController alloc]init];
[vc triggerSuccess];
} errorBlock:^(NSError *error) {
ViewController * vc = [[ViewController alloc]init];
[vc uploadFail:error];
}];
}
in the VC i have tried the following:
- (void)triggerSuccess
{
[self segueToSuccess];
}
- (void)segueToSuccess
{
[self hideMessage];
[self.navigationController performSegueWithIdentifier:#"approveSegue" sender:self];
}
As well as:
- (void)triggerSuccess
{
[self segueToSuccess];
}
- (void)segueToSuccess
{
[self hideMessage];
UIViewController *controller = [self.storyboard instantiateViewControllerWithIdentifier:#"done"];
[self.navigationController pushViewController:controller animated:YES];
}
In a moment of pure desperation i even tried:
- (void)triggerSuccess
{
[self segueToSuccess];
}
- (void)segueToSuccess
{
[self hideMessage];
//[self.navigationController performSegueWithIdentifier:#"approveSegue" sender:self];
[self dismissViewControllerAnimated:NO completion:nil];
[self.navigationController popToRootViewControllerAnimated:NO];
[self performSelector:#selector(segueToSuccessPart2) withObject:nil afterDelay:0.25];
}
- (void)segueToSuccessPart2
{
UIViewController *controller = [self.storyboard instantiateViewControllerWithIdentifier:#"done"];
[self.navigationController pushViewController:controller animated:YES];
}
I've obviously missed something, and i'm guessing it's to do with the application going into the background and the VC being "unloaded" from memory, and needing re-instatiating, but i'm not sure where to begin with that.
Any help would be greatly appreciated as i'm about to throw the computer out of the window . .
Thanks
Gareth
Edit 1
After doing some more troubleshooting it appears that during this call in the VC:
[self dismissViewControllerAnimated:NO completion:nil];
[self.navigationController popToRootViewControllerAnimated:NO];
self.navigationController is nil . . .
I'm guessing that is likely the cause of the issues i'm seeing?
Edit 2
So as suggested by Kelin, i am trying to make sure i retain the Navigation Controller.
I have done the following in AppDelegte:
#property (nonatomic, strong) UINavigationController *navController;
and
#synthesize navController;
But when i try to access this from the VC using the below code, it's still nil . .
AppDelegate *appDelegate = [[UIApplication sharedApplication]delegate];
UINavigationController *navController = appDelegate.navController;
[self dismissViewControllerAnimated:NO completion:nil];
[navController popToRootViewControllerAnimated:NO];
Edit 3
I have also added this to the AppDelegate, which means the Navigation Controller is no longer nil. But still nothing happens . . .
if (!self.navController)
{
self.navController = [[UINavigationController alloc]initWithNibName:#"Main" bundle:nil];
}

Answer 1

The problem is you trying to perform segue from storyboard using programmatically created View Controller.
You use -performSegueWithIdentifier: sender: completely wrong. In this method "sender" is a button, or any other control which action initialises segue, but not the view controller to be pushed.
Usually segue is created with storyboard. But if you really need to create it manually, call:
-[UIStoryboardSegue initWithIdentifier:source:destination:]
where source and destination are view controllers.
Read this: https://developer.apple.com/library/ios/recipes/xcode_help-interface_builder/articles-storyboard/StoryboardSegue.html
or this (about custom segues):

Answer 2

You can not do both dismiss and pop together either you have to pop or dismiss the view controller and
Every ViewController have it's own NavigationController which is default point out to navigation controller you added to AppDelegate.
So, You also can access it by self.navigationController (Edit 3)
Also check whether you initialised navigation controller in
AppDelegate
self.navController = [[UINavigationController alloc] initWithRootViewController:firstVC];