iOS: Remove last image in array after touchesEnded has been completed - ios

Question

I am building an iOS drawing application and I am trying to implement a undo button to remove the line drawn by the user. I've created an array of images in a variable:
var images = [UIImage]()
Each time the user swipes and removes the finger from the screen a new image is created in the touchesEnded function. I think I need to remove the last image to get the previous image in an IBAction which will act as a undo button.
Here's a sample of my current code:
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first!
guard touch.view != floaty else { return }
swiped = false
if let touch = touches.first{
postBtn.isEnabled = true
postBtn.setImage(UIImage(named: "done_icon_moved"), for: .normal)
dismissBtn.isEnabled = true
undoBtn.isEnabled = true
undoBtn.setImage(UIImage(named: "undo_icon_moved"), for: .normal)
lastPoint = touch.location(in: self.view)
}
}
func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint) {
// 1
UIGraphicsBeginImageContext(view.frame.size)
tempImageView.image?.draw(in: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height))
let context = UIGraphicsGetCurrentContext()
// 2
context?.move(to: CGPoint(x: fromPoint.x, y: fromPoint.y))
context?.addLine(to: CGPoint(x: toPoint.x, y: toPoint.y))
// 3
context?.setBlendMode(CGBlendMode.normal)
context?.setLineCap(CGLineCap.round)
context?.setLineWidth(brushWidth)
context?.setStrokeColor(UIColor(red:red, green:green, blue:blue, alpha: 1.0).cgColor)
// 4
context?.strokePath()
// 5
tempImageView.image = UIGraphicsGetImageFromCurrentImageContext()
tempImageView.alpha = opacity
UIGraphicsEndImageContext()
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
swiped = true
if let touch = touches.first {
let currentPoint = touch.location(in: view)
drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint)
lastPoint = currentPoint
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
if !swiped {
// draw a single point
drawLineFrom(fromPoint: lastPoint, toPoint: lastPoint)
}
// Merge tempImageView into mainImageView
UIGraphicsBeginImageContext(mainImageView.frame.size)
mainImageView.image?.draw(in: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height),blendMode: CGBlendMode.normal, alpha: 1.0)
tempImageView.image?.draw(in: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height), blendMode: CGBlendMode.normal, alpha: opacity)
mainImageView.image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
tempImageView.image = nil
print("touch ended")
}

Answer 1

Check if image array have objects or not before remove last object.
if images.count != 0 {
images.removeLast()
}