Pan Segue Calls viewDidLoad Loop - ios

Question

My pan gesture programmatically fakes a button press. If you press the actual button, the VC's viewDidLoad runs again once, stops, and is fine. But when I use the pan-gesture to programmatically fake the button press, the viewDidLoad runs about seven times, then stops.
The right-edge gesture triggers the "tomorrow" state which loads a handful of times. At that point, a left-edge gesture triggers the "today" state. That also loads 4-5 times.
Any ideas? Some code below, if needed.
Pan gesture added in viewDidLoad:
//Adds edge gesture depending on VC state
if curMainList == "Today" {
let panLeftEdgeGesture_MainVC = UIScreenEdgePanGestureRecognizer(target: self, action: "panLeftEdge_toLifeList:")
panLeftEdgeGesture_MainVC.edges = .Left
view.addGestureRecognizer(panLeftEdgeGesture_MainVC)
let panRightEdgeGesture_MainVC = UIScreenEdgePanGestureRecognizer(target: self, action: "panFromRightEdgeAction:")
panRightEdgeGesture_MainVC.edges = .Right
view.addGestureRecognizer(panRightEdgeGesture_MainVC)
self.footer_LeftBtn.addTarget(self, action: "LeftFooterBtnPress", forControlEvents: UIControlEvents.TouchUpInside)
}
else {
let panLeftEdgeGesture = UIScreenEdgePanGestureRecognizer(target: self, action: "panFromLeftEdgeAction:")
panLeftEdgeGesture.edges = .Left
view.addGestureRecognizer(panLeftEdgeGesture)
}
Gesture's triggered:
//Gestures visible when view is 'Today'
func panLeftEdge_toLifeList(sender: UIScreenEdgePanGestureRecognizer) {
dispatch_async(dispatch_get_main_queue()) { () -> Void in
self.performSegueWithIdentifier("segueToLifeLists", sender: nil)
}
}
func panFromRightEdgeAction(sender: UIScreenEdgePanGestureRecognizer) {
//self.tomHdrBtnPress(tomorrowHdr)
tomorrowHdr.sendActionsForControlEvents(UIControlEvents.TouchUpInside)
}
//Gesture added when viewing 'Tomorrow' list
func panFromLeftEdgeAction(sender: UIScreenEdgePanGestureRecognizer) {
//self.todayHdrBtnPress(todayHdr)
todayHdr.sendActionsForControlEvents(UIControlEvents.TouchUpInside)
}
#IBAction func todayHdrBtnPress(sender: AnyObject) {
UIView.animateWithDuration(0.75, animations: {
//Header changes
self.hdrBox.backgroundColor = UIColor(red: 46/255.0, green: 173/255.0, blue: 11/255.0, alpha: 1.0)
self.footer_RightArrow.hidden = false
self.footer_RightBtn.hidden = false
}
, completion: nil
)
curMainList = "TodayTask"
currentListEntity = curMainList
viewDidLoad()
}
#IBAction func tomHdrBtnPress(sender: AnyObject) {
UIView.animateWithDuration(0.75, animations: {
//Header changes
self.hdrBox.backgroundColor = UIColor(red: 49/255.0, green: 82/255.0, blue: 171/255.0, alpha: 1.0)
self.footer_LeftBtn.addTarget(self, action: "LeftFooterBtnPress", forControlEvents: UIControlEvents.TouchUpInside)
}
, completion: nil
)
curMainList = "TomTask"
currentListEntity = curMainList
viewDidLoad()
}

Answer 1

The problem is that pan gestures are continuous gestures (meaning that as you move your finger, the handler is called repeatedly). For a pan gesture, it's called once with a gesture.state of .Began, repeated with a state of .Changed as the user's finger moves, and the finally with a state of .Ended or .Cancelled when the user stops the gesture.
So, you generally would not trigger an animateWithDuration from a continuous gesture. You just update the state based upon, for example, gesture.translationInView() or what have you. Just update the views immediately to reflect the updated pan and it's called so frequently, that it ends up rendering something that feels like an animation, but it's really just a sequence of updates linked to continuous flow of updates your gesture recognizer's handler receives as the user progresses in their gesture.
The only time you would animate within a continuous gesture is upon .Ended or .Cancelled, to complete the animation. For example, maybe the user drags their finger half way across, so on .Changed you just update the view immediately without any animation, but when they lift their finger (i.e. the gesture handler receive .Ended), you might animate completion to the view's final state.
Bottom line, the handling in gesture recognizers is a very different mechanism for animation that might result from a button (in which you call the animateWithDuration methods once to initiate an animation that UIKit then takes care of for you). It's best not to conflate these two very different ways of updating/animating the UI.
You also are performing a segue in one of your pan handlers. If you want to have a segue performed interactively as you pan, you should refer to WWDC 2013 video Custom Transitions Using View Controllers, which shows how you can combine an animation controller (which dictates the nature of the animation) with an interaction controller (which links the progress of the gesture with the animation controller). But in this pattern, you perform the segue once and only once, and merely update the UIPercentDrivenInteractiveTransition in the gesture, which will link the progress of the transition with the user's finger.
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