Custom Fade Segue not animating if I present the destinationViewController - ios

Question

I've written a custom segue to get a fade effect, which i'm trying to achieve by inserting the destination view controller below the source view controller and animating the alpha of the source view controller to zero.
However, adding the destination view controller below the source seems to cancel the animation and the segue performs as if it is a regular present with animation disabled.
import UIKit
class FadeSegue: UIStoryboardSegue {
override func perform() {
// Get the view of the source
let sourceViewControllerView = self.sourceViewController.view
// Get the view of the destination
let destinationViewControllerView = self.destinationViewController.view
let screenWidth = UIScreen.mainScreen().bounds.size.width
let screenHeight = UIScreen.mainScreen().bounds.size.height
// Make the destination view the size of the screen
destinationViewControllerView.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
if let window = UIApplication.sharedApplication().keyWindow {
// Insert destination below the source
// Without this line the animation works but the transition is not smooth as it jumps from white to the new view controller
window.insertSubview(destinationViewControllerView, belowSubview: sourceViewControllerView)
// Animate the fade, remove the destination view on completion and present the full view controller
UIView.animateWithDuration(0.4, animations: {
sourceViewControllerView.alpha = 0.0
}, completion: { (finished) in
destinationViewControllerView.removeFromSuperview()
self.sourceViewController.presentViewController(self.destinationViewController, animated: false, completion: nil)
})
}
}
}

Answer 1

Hello I think that what you need is this
override func perform() {
// Get the view of the source
let sourceViewControllerView = self.sourceViewController.view
// Get the view of the destination
let destinationViewControllerView = self.destinationViewController.view
let screenWidth = UIScreen.mainScreen().bounds.size.width
let screenHeight = UIScreen.mainScreen().bounds.size.height
// Make the destination view the size of the screen
destinationViewControllerView.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
// Insert destination below the source
// Without this line the animation works but the transition is not smooth as it jumps from white to the new view controller
destinationViewControllerView.alpha = 0;
sourceViewControllerView.addSubview(destinationViewControllerView);
// Animate the fade, remove the destination view on completion and present the full view controller
UIView.animateWithDuration(10, animations: {
destinationViewControllerView.alpha = 1;
}, completion: { (finished) in
destinationViewControllerView.removeFromSuperview()
self.sourceViewController.presentViewController(self.destinationViewController, animated: false, completion: nil)
})
}
}
I Hope this help you

Answer 2

The slightly modified Swift 4.1 compatible solution based on the answer from #reinier-melian
/// Performs a simple fade between source and destination view controller.
class Fade: UIStoryboardSegue {
override func perform() {
guard let destinationView = self.destination.view else {
// Fallback to no fading
self.source.present(self.destination, animated: false, completion: nil)
return
}
destinationView.alpha = 0
self.source.view?.addSubview(destinationView)
UIView.animate(withDuration: CATransaction.animationDuration(), animations: {
destinationView.alpha = 1
}, completion: { _ in
self.source.present(self.destination, animated: false, completion: nil)
})
}
}

Answer 3

This is what I ended up doing for my purposes. It puts a placeholder view with basic ui elements over the top once all the on screen things have animated out and fades in the placeholder, then presents the destination view controller and removes the placeholder. The destination view controller then animates in all its elements, essentially making the transition invisible and looks like one single animation:
import UIKit
class FadeSegue: UIStoryboardSegue {
var placeholderView: UIViewController?
override func perform() {
let screenWidth = UIScreen.mainScreen().bounds.size.width
let screenHeight = UIScreen.mainScreen().bounds.size.height
if let placeholder = placeholderView {
placeholder.view.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
placeholder.view.alpha = 0
sourceViewController.view.addSubview(placeholder.view)
UIView.animateWithDuration(0.4, animations: {
placeholder.view.alpha = 1
}, completion: { (finished) in
self.sourceViewController.presentViewController(self.destinationViewController, animated: false, completion: {
placeholder.view.removeFromSuperview()
})
})
} else {
self.destinationViewController.view.alpha = 0.0
self.sourceViewController.presentViewController(self.destinationViewController, animated: false, completion: {
UIView.animateWithDuration(0.4, animations: {
self.destinationViewController.view.alpha = 1.0
})
})
}
}
}
and the unwind:
import UIKit
class FadeSegueUnwind: UIStoryboardSegue {
var placeholderView: UIViewController?
override func perform() {
let screenWidth = UIScreen.mainScreen().bounds.size.width
let screenHeight = UIScreen.mainScreen().bounds.size.height
if let placeholder = placeholderView {
placeholder.view.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
placeholder.view.alpha = 0
sourceViewController.view.addSubview(placeholder.view)
UIView.animateWithDuration(0.4, animations: {
placeholder.view.alpha = 1
}, completion: { (finished) in
self.sourceViewController.dismissViewControllerAnimated(false, completion: nil)
})
} else {
self.destinationViewController.view.alpha = 0.0
self.sourceViewController.dismissViewControllerAnimated(false, completion: {
UIView.animateWithDuration(0.4, animations: {
self.destinationViewController.view.alpha = 0.0
})
})
}
}
}