Removing a view controller from memory when instantiating a new view controller

Question

In my app, I am instantiating new view controllers instead of using segues because it looks better in animations as a result, my views keep running in the background. This causes large memory leaks.

My code to go back to the main screen is:

let mainStoryboard = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle())
        let vc  : UIViewController = mainStoryboard.instantiateViewControllerWithIdentifier("MainScreen") as UIViewController
        self.presentViewController(vc, animated: false, completion: nil)

This view controller is still active in the background and therefore shouldn't be instantiated again. How do I do this.

When I close my view controller using the above code, it also does not unload it, it keeps running in the background. How do I make it unload as soon as the screen disappears.

I have tried doing

override func viewDidDisappear(animated: Bool) {
    super.viewDidDisappear(animated)
    view.removeFromSuperview()
    view = nil
}

However this does not work properly. How do I properly destroy a view controller from memory when exiting a view controller in this manner.

Answer 1

An important reason for this problem is related to the memory management!

if you have 'strong reference' or 'delegate' or 'closure' or other things like this, and you didn't managed these objects, your view controller has strong reference and never be closed.

you should get 'deinit' callback in view controller after than viewDidDisappear called. if 'deinit' not called so your view controller still is alive and it has strong reference.