UIView removeFromSuperview calls didMoveToSuperview

Question

I do not understand why UIView removeFromSuperviewcalls didMoveToSuperview.

I think that didMoveToSuperviewis called only when the view is added to the view. Can someone explain this why it removeFromSuperviewcauses didMoveToSuperview?

Here is what I do in removeFromSuperview:

public override func removeFromSuperview() {

    clearDelegates()

    chaosPad?.removeFromSuperview()
    brushSliders?.removeFromSuperview()
    moodSlider?.removeFromSuperview()
    brushShapeMenu?.removeFromSuperview()
    moodMenu?.removeFromSuperview()
    gravityMenu?.removeFromSuperview()
    rotationMenu?.removeFromSuperview()

    menuGroups = []
    centerButtons = []
    scrollMenuItems = []
    menu?.removeFromSuperview()
    menu = nil

    super.removeFromSuperview()
}

func clearDelegates() {
    chaosPad?.delegate = nil
    viewController = nil
}

Here is the call stack showing how it is called didMoveToSuperview:

#0  0x0000000110f39708 in specialized _fatalErrorMessage(StaticString, StaticString, StaticString, UInt) -> () ()
#1  0x000000010b9cb960 in TDTOilistMenuPainting.configureFrames() -> () at /FastDev/TDTPhotoLib/Oilist/Classes/TDTOilistMenuPainting.swift:161
#2  0x000000010b9cb83e in TDTOilistMenuPainting.didMoveToSuperview() -> () at /FastDev/TDTPhotoLib/Oilist/Classes/TDTOilistMenuPainting.swift:146
#3  0x000000010b9cb872 in @objc TDTOilistMenuPainting.didMoveToSuperview() -> () ()
#4  0x000000010f5d1db5 in __45-[UIView(Hierarchy) _postMovedFromSuperview:]_block_invoke ()
#5  0x000000010dc87c60 in -[NSISEngine withBehaviors:performModifications:] ()
#6  0x000000010f5d19b1 in -[UIView(Hierarchy) _postMovedFromSuperview:] ()
#7  0x000000010f5cf610 in __UIViewWasRemovedFromSuperview ()
#8  0x000000010f5cf107 in -[UIView(Hierarchy) removeFromSuperview] ()
#9  0x000000010b9c9aba in TDTOilistMenuPainting.removeFromSuperview() -> () at /FastDev/TDTPhotoLib/Oilist/Classes/TDTOilistMenuPainting.swift:73
#10 0x000000010ba6d269 in TDTPaintingViewController.(navigationController(UINavigationController, animationControllerForOperation : UINavigationControllerOperation, fromViewController : UIViewController, toViewController : UIViewController) -> UIViewControllerAnimatedTransitioning?).(closure #2) at /FastDev/TDTPhotoLib/Oilist/Classes/TDTPaintingViewController.swift:2706

Answer 1

. didMoveToSuperview , viewlook, nil. , , , , :

override func didMoveToSuperview() {
    if let superview = self.superview {
        // the view was added as a subview to superview
    }
    else {
        // the view was removed from its superview
    }
}