Hello, I have a question. Are there any memory lea...

# kotlin-native

[Arkadii Ivanov]

Hello, I have a question. Are there any memory leaks in the following code? This view controller is created and used from Swift.

fun myViewController(): UIViewController = MyViewControllerImpl()

private class MyViewControllerImpl : UIViewController(nibName = null, bundle = null) {
    private val button = UIButton()
    
    override fun viewDidLoad() {
        super.viewDidLoad()

        button.addTarget(target = this, action = sel_registerName("onClick"), forControlEvents = UIControlEventTouchUpInside)
        view.addSubview(button)
    }
    
    @ObjCAction
    private fun onClick() {
    }
}

[Sam]

No. Addtarget doesn't retain the object being sent to it. The only thing I would critique is that you're creating a view at construction time (button). Another more proper way of doing that is to override loadView. View controllers have a life cycle that doesn't always involve having a view created. On modern devices it isn't all that necessary to worry about, maybe on older ones running newer iOS versions but probably not.

[Arkadii Ivanov]

Alright. What if addTarget would retain the reference. In this case would it be a memory leak?

[Sam]

If it did yes. You would have VC -> button and button -> VC. Although K/N does do some garbage collection so it may be smart enough to break the retain cycle. In straight Swift or objc it would definitely be a leak. You're more likely to find leaks using blocks and passing them off to other objects that keep the block around for a while.

[Arkadii Ivanov]

This is the question. In Swift we have deinit and weak var. In Kotlin we don't have any. How to deal with cyclic references in such cases (when the class is created and used from Swift)?

[Sam]

There's a weak reference in K/N. https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.native.ref/-weak-reference/index.html

[Arkadii Ivanov]

That's makes sense, thanks!