Why ARC is not deallocating memory after popViewController

Question

I\'m pushing and popping ViewControllers in UINavigationController.

I\'m tracking the memory consumption of my app. While pushing the new viewController the memory consu

Answer 1

When you dismiss a view controller (or pop it), it will be deallocated if you didn't make any strong pointers to it (that controller is retained by the navigation controller, or the presenting view controller, so you usually don't need to have a pointer to it when you create it and push or present it).

It will be be released if there are no other strong pointers to it

Answer 2

If your app design allows the user to push and pop the same view controller over and over again, you may want to look at reusing the same view controller and just updating its contents each time it's pushed.

Instead of creating and destroying it over and over, create one, set up its contents and push, when it's popped, keep it around ready to be shown again. Next time it needs to be shown, update its contents and then push it again.

Answer 3

I think you get an error, when you try to pop the view controller because the navigation controller does not have a valid reference to the view controller, as it was released after you pushed it.

Answer 4

Consider reviewing whether you are referencing self in a block. If you do, you risk holding onto the UIViewController reference after you have popped it.

For a more in-depth review of why, check out this answer: How do I avoid capturing self in blocks when implementing an API?

Answer 5

Make sure your viewcontroller (A) has no reference of any other viewcontroller (B) or any object it has. Incase it has then make sure that VC-B is not referencing back VC-A. If it has some reference back to VC-A then make it a weak property. Otherwise strong retain cycle will keep the VC in memory even if its popped.

• Another thing is to check wether theres any closure in your VC, check its body if it is referencing any property or method with self then make a Capture list to avoid retain cycle as "Closures are Reference Types"

• Check if theres any NSNotification observer you are not releasing

• Make a print call in deinit method to check wether its deallocated.

For further understanding on memory management:

• https://medium.com/mackmobile/avoiding-retain-cycles-in-swift-7b08d50fe3ef
• https://www.youtube.com/watch?v=GIy-qnGLpHU

Answer 6

You should use an unwind segue instead of popping.