presentViewController() pops the view behind the last view - ios

Question

I'm trying to perform a transition to another UIViewController in another storyboard but the problem is that the view that I want to display pops behind the view where I'm from.
I know that because my app includes a Snapchat-like navigation between views, so I can drag the view to the left or the right and I can see the view behind.
Here is how I attempt to do that :
#IBAction func account(sender: UIButton) {
if self._isOnline {
self.pageController?.reverseViewControllerAnimated(true)
}
else {
let alertView = UIAlertController(title: "blablablabla", message: "blablablabla", preferredStyle: .Alert)
alertView.addAction(UIAlertAction(title: "No", style: .Cancel, handler: nil))
alertView.addAction(UIAlertAction(title: "Yes", style: .Default, handler: { (alertAction) -> Void in
let storyboard = UIStoryboard(name: "SignUpLogin", bundle: NSBundle.mainBundle())
let vc = storyboard.instantiateInitialViewController() as! UIViewController
self.presentViewController(vc, animated: false, completion: nil)
}))
presentViewController(alertView, animated: true, completion: nil)
}
}
With SignUpLogin that is the name of my second .storyboard file, here I'm in Heart.storyboard.
The action takes place in a UIAlertController, if the user press no, nothing append, if he press yes he's supposed to be redirected to the initial view of my SignUpLogin.storyboard file.
My problem come from the view at the bottom left corner. And if I use the code above in the view at the top right corner, that works ! Why ?
I have no idea of how I can do differently.

Answer 1

I've found the solution to my problem !
#IBAction func account(sender: UIButton) {
if self._isOnline {
self.pageController?.reverseViewControllerAnimated(true)
}
else {
let alertView = UIAlertController(title: Constants.LocalizedJoinOurBand, message: Constants.LocalizedNeedToCreatAnAccount, preferredStyle: .Alert)
alertView.addAction(UIAlertAction(title: Constants.LocalizedNo, style: .Cancel, handler: nil))
alertView.addAction(UIAlertAction(title: Constants.LocalizedYes, style: .Default, handler: { (alertAction) -> Void in
if let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate {
let storyboard = UIStoryboard(name: "SignUpLogin", bundle: NSBundle.mainBundle())
let vc = storyboard.instantiateInitialViewController() as! UIViewController
UIApplication.sharedApplication().keyWindow?.rootViewController = vc
}
}))
presentViewController(alertView, animated: true, completion: nil)
}
}
I don't know why in this case particularly but I have to directly set the rootViewController of my AppDelegate with this line :
UIApplication.sharedApplication().keyWindow?.rootViewController = vc