Aim

Understand retain cycle when working with closures in swift

Pre-setup

Follow the steps to setup a alert when a ViewController is deallocated:

In Xcode, go to the Breakpoint navigator (Cmd+8)
At the bottom-left on the screen, tap '+', then select "Symbolic Breakpoint..." from the menu
Fill the form:
- Name: UIViewController dealloc
- Symbol: -[UIViewController dealloc]
- Module: UIKitCore (or leave empty)
- Condition: !(BOOL)([[$arg1 description] containsString:@"Input"]) to exclude UIInputViewController, UICompatibilityInputViewController, etc.
- Ignore: leave at zero
- Action: Select "Log Message"
- Enter: --- dealloc @(id)[$arg1 description]@ @(id)[$arg1 title]@ (or customize as needed)
- Select "Log message to console"
- Next to "Action: Log Message", tap on '+' to add a new Action
- Select: "Sound" and choose any sound from the list (Submarine, Pop...)
- Check "Automatically continue after evaluating actions" so Xcode does not stop at the breakpoint

Move onto the second screen, and wait for the callback to be received (check the logs)
Press the back button. Nothing really happened.
Now uncomment the code inside lazy var delayViewModel = DelayViewModel and re-run the app.
Go to the second screen, wait for the callback, and then press back.
If your Pre-setup was successful, you should hear a sound with the text in the logs:

--- dealloc @"<MemoryManagementTest.CallbackViewController: 0x1032133f0>" 0x0

This means the CallbackViewController was deallocated successfully.