Is there a straightforward way to add a UIButton click listener in Kotlin IOS?

Question

The signature for addTarget (in Kotlin) is:

public open external expect fun addTarget(
    target: Any?,
    action: COpaquePointer? /* = CPointer<out CPointed>? */,
    forControlEvents: UIControlEvents /* = ULong */
): Unit

I think I get how I'd hand in a C function pointer, but that doesn't seem to be the case here...?

Answer 1

Found the solution here: https://discuss.kotlinlang.org/t/how-to-call-a-selector-from-kotlin-for-ios/4591

The key is to use sel_registerName to create the pointer and to annotate the target with @ObjCAction:

import kotlinx.cinterop.ObjCAction
import platform.UIKit.*
import platform.objc.sel_registerName

class MyClass() {

    val uiButton = UIButton.buttonWithType(UIButtonTypeSystem)

    init {
        uiButton.setTitle("Click me", UIControlStateNormal)
        uiButton.addTarget(this, sel_registerName("clicked"), UIControlEventTouchUpInside)
    }

    @ObjCAction
    fun clicked() {
       // React to click here...
    }

}