Custom Segue in Swift

Question

@objc(SEPushNoAnimationSegue)
class SEPushNoAnimationSegue: UIStoryboardSegue {
    override func perform () {
      self.sourceViewController.navigationController.pushViewController(self.destinationViewController, animated:false)
    }
}

In the above code, I have 2 questions: 1). it has a compile error: 'UINavigationController!' does not have a member named 'pushViewController'

But in that class, it did has a pushViewController method.

2). I have to add the annotation: @objc(SEPushNoAnimationSegue), otherwise, in storyboard, it only recognize the random generated name, like, _tcxxxxSEPushNoAnimationSegue.

why these 2 issues happen here?

Answer 1

Issue #1

UIStoryboardSegue has an irritating flaw: its sourceViewController and destinationViewController properties are typed as AnyObject! (that's the case even in Objective-C (Id type)) and not as UIViewController, as it should be.

That same flaw creates havoc in your perfect and simple code. Here's how to rewrite it in order to fix the compile errors:

@objc(SEPushNoAnimationSegue)
class SEPushNoAnimationSegue: UIStoryboardSegue {
    override func perform () {
        let src = self.sourceViewController as UIViewController
        let dst = self.destinationViewController as UIViewController
        src.navigationController.pushViewController(dst, animated:false)
    }
}

NOTE: Apple fixed this thing in iOS 9. sourceViewController and destinationViewController are now correctly declared as UIViewController.

Issue #2

The Swift compiler stores its symbols using its own name mangling, and good ol' Objective-C does not recognize it in Xcode. Using an explicit @obj() solves the issue.