memory leak when using images in Swift? - ios

Question

I have a very simple app with two viewControllers at the moment. I have a transition between them (with a segue of course) and both screens have a lot of images and buttons with images.
What I discovered was that there is a memory leak when you alternate between the screens. I am guessing, that somehow the images are loaded again each time you open the viewController again. Around 6MB is added each time and I am pretty sure that the images are less than 1MB in total. So maybe there is something else craving all the memory?
I have 6 image Views and I use the cross dissolve transition in the default modus. I wish I could copy some code here, but it is a big project and I would not know what code would be helpful.
So my question would be: what is causing this problem (and preferable how can I fix this)? Is it the images, or maybe the segues with the transition.
Any help would be really appreciated! Thanks!
--- Edit: Here's some bits of code with the images
// variables of the bottom menu bar
#IBOutlet weak var cameraButton: UIButton!
#IBOutlet weak var redoButton: UIButton!
#IBOutlet weak var saveButton: UIButton!
#IBOutlet weak var shareButton: UIButton!
#IBOutlet weak var overLay: UIImageView!
// this function lets the statusbar disappear
override func prefersStatusBarHidden() -> Bool {
return true
}
override func viewDidLoad() {
super.viewDidLoad()
overLay.image = nil
// variables for accessing web images
let url = NSURL(string: "http://www.fteunen.com/app/overLay.png")
let urlRequest = NSURLRequest(URL: url!)
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue.mainQueue(), completionHandler: {
response, data, error in
if error != nil {
println("Something happened i guess, not good!!")
} else {
//let image = UIImage(data: data)
self.overLay.image = UIImage(data: data)
}
})
}
And I don't know where I can find code from the segues. I just clicked on some options for that.
---- EDIT: The second viewController (the one with all the images) and the dismissViewController:
class ViewController2: UIViewController {
// variables of the bottom menu bar
#IBOutlet weak var cameraButton: UIButton!
#IBOutlet weak var redoButton: UIButton!
#IBOutlet weak var saveButton: UIButton!
#IBOutlet weak var shareButton: UIButton!
#IBOutlet weak var overLay: UIImageView!
// this function lets the statusbar disappear
override func prefersStatusBarHidden() -> Bool {
return true
}
override func viewDidLoad() {
super.viewDidLoad()
overLay.image = nil
// variables for accessing web images
let url = NSURL(string: "http://www.fteunen.com/app/overLay.png")
let urlRequest = NSURLRequest(URL: url!)
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue.mainQueue(), completionHandler: {
response, data, error in
if error != nil {
println("Something happened i guess, not good!!")
} else {
//let image = UIImage(data: data)
self.overLay.image = UIImage(data: data)
}
})
}
override func viewDidLayoutSubviews() {
//code
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func didTakePhoto(sender: AnyObject) {
//code
})
}
override func dismissViewControllerAnimated(flag: Bool, completion: (() -> Void)?) {
dismissViewControllerAnimated(true) {
// Optional completion handler code here
}
}
#IBAction func redoPicture(sender: AnyObject) {
// code
})
}

Answer 1

You are leaking memory because you are continuously creating new view controllers which are all essentially piling on top of each other and downloading images. You should perform a segue and then dismiss that view controller to return to the previous view controller. In your second view controller where you are trying to segue back to the first controller call dismissViewControllerAnimated in either of the following ways:
dismissViewControllerAnimated(true, completion: nil)
or:
dismissViewControllerAnimated(true) {
// Optional completion handler code here
}

Answer 2

Memory Leak due to constantly creating new VC ontop of VC
Use Unwind.
In MainViewController
#IBAction unwindSegue(segue: UIStoryboardSegue, sender: UIStoryboardSegue){//any code you want executed upon return to mainVC}
In NewViewController
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?){//pass any information from New to Main here}
Then, in NewVC, simply control+drag from whichever UIButton you want to cause the unwind to NewVC's Exit symbol and select unwindSegue
*
*
NOTE: Also if you want the unwind to happen programmatically instead of from a Button. Control+drag from NewVC (yellow button) to exit(red-orange button)
, this will create an unwind segue under "Exit". Select this "Unwind segue" and in attributes inspector give it an identifier.
Now in NewVC create a function
func NameYourFunc(){performSegueWithIdentifier("TheIdentiferYouUsed", sender: self)}
and anywhere in your NewVC code when you want to perform this unwind simply call NameYourFunc()