Here is a modified code from the documentation example
https://www.swift.org/documentation/server/guides/memory-leaks-and-usage.html#troubleshooting :
class ViewController: UIViewController {
var closure: () -> Void = { () }
public func doNothing() {}
public func doSomethingThatLeaks() {
self.closure = {
// This will leak as it'll create a permanent reference cycle:
//
// self -> self.closure -> self
self.doNothing()
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Memory leak example:
doSomethingThatLeaks()
// Abandoned memory example:
// NotificationCenter.default.addObserver(forName: .init("Abandoned"), object: nil, queue: nil) { _ in
// print("\(self)")
// }
}
deinit {
print(#function, Self.self)
}
}
If you place it, for example, in a navigation controller, do a push-pop several times, deinit will not be printed.
But if you look in the Debug Memory Graph, it will not even show that there is a strong reference to this controller:
Only if you manually select:
You can see that it is held by the closure context, which it holds:
This is definitely not abandoned memory (like the commented piece of the code example), but it is not shown either in the Debug Memory Graph or in Instruments Leaks.
Why?
VAndrJ
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