How to prevent subview release self after call removeFromSuperview? - ios

Question

I want to change with two subviews as button been clicked, the subview was created by StoryBoard, each subview has a button, click the button will bring another subview and hidden current one.
But I found when a subview call removeFromSuperview(), it will be release automatically, if I want to use this subview later, I need a var to point it.
Here is my code:
class ViewController: UIViewController {
#IBOutlet weak var secondView: UIView!
#IBOutlet weak var firstView: UIView!
var temp1: UIView?
var temp2: UIView?
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
temp1 = firstView
temp2 = secondView
secondView.removeFromSuperview()
}
#IBAction func moveToSecond(_ sender: UIButton) {
firstView.removeFromSuperview()
view.insertSubview(secondView, at: 0)
secondView.isUserInteractionEnabled = true
}
#IBAction func moveToFirst(_ sender: UIButton) {
secondView.removeFromSuperview()
view.insertSubview(firstView, at: 0)
firstView.isUserInteractionEnabled = true
}
}
Without two temp var, subview will release after removeFromSuperview, and cause next insertSubview crash because it is nil.
So, How to prevent subview auto release?
Is there another way to change between two subviews created by StoryBoard graceful?
My mistake, I didn't notice that outlet is weak, everything is reasonable, when removeFromSuperview, no strong point is left to the sub view, than it release automatically.

Answer 1

You can use #IBOutlet var secondView: UIView! to create strong reference of the view.But as per your requirement I suggest not to remove it from the super view. Instead of that you should hide and show the views when needed as below.
class ViewController: UIViewController {
#IBOutlet var secondView: UIView!
#IBOutlet var firstView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
secondView.isHidden = true
}
#IBAction func moveToSecond(_ sender: UIButton) {
firstView.isHidden = true
secondView.isHidden = false
secondView.isUserInteractionEnabled = true
}
#IBAction func moveToFirst(_ sender: UIButton) {
secondView.isHidden = true
firstView.isHidden = false
firstView.isUserInteractionEnabled = true
}
}

Answer 2

Assuming your two views are one upon above , having same width and same height . In viewDidLoad . first set the firstView to front and secondView to back. Once button click i bring secondView to front and firstView to back , like so on.
import UIKit
class ViewController1: UIViewController {
#IBOutlet var secondView: UIView!
#IBOutlet var firstView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
self.view.bringSubview(toFront: firstView)
self.view.sendSubview(toBack: secondView)
}
#IBAction func moveToSecond(_ sender: UIButton) {
self.view.bringSubview(toFront: secondView)
self.view.sendSubview(toBack: firstView)
}
#IBAction func moveToFirst(_ sender: UIButton) {
self.view.bringSubview(toFront: firstView)
self.view.sendSubview(toBack: secondView)
}
}
If your two sub view's are in different position of the view. then you need to hide alternative View in respective button click
class ViewController: UIViewController {
#IBOutlet var secondView: UIView!
#IBOutlet var firstView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
secondView.isHidden = true
firstView.isUserInteractionEnabled = true
}
#IBAction func moveToSecond(_ sender: UIButton) {
firstView.isHidden = true
secondView.isHidden = false
secondView.isUserInteractionEnabled = true
}
#IBAction func moveToFirst(_ sender: UIButton) {
secondView.isHidden = true
firstView.isHidden = false
firstView.isUserInteractionEnabled = true
}
}