Fragment View Binding Delegate

FragmentAutoClearedValueBinding.kt

class FragmentAutoClearedValueBinding<T : ViewBinding>(
    val binder: (View) -> T
) : ReadOnlyProperty<Fragment, T>,
    DefaultLifecycleObserver {

    private var value: T? = null

    override fun onDestroy(owner: LifecycleOwner) {
        value = null // Clear reference.
    }

    override fun getValue(thisRef: Fragment, property: KProperty<*>): T {
        return value ?: binder(thisRef.requireView()).also {
            setValue(thisRef, it)
        }
    }

    private fun setValue(fragment: Fragment, value: T) {
        fragment.viewLifecycle.removeObserver(this)
        this.value = value
        fragment.viewLifecycle.addObserver(this)
    }
}

ViewBindingExt.kt

fun <T : ViewBinding> Fragment.viewBindingWithBinder(
    binder: (View) -> T
) = FragmentAutoClearedValueBinding(binder)

should it be fragment.lifecycle in newer kotlins ?

Not entirely sure about that. (I use kotlin 1.6.10.)

When I use the lifecycle instead of viewLifeCycle, the code does compile.
Bit it seems the onDestroy method is never called. And when you have two fragments on a stack and press the back button, the bindings are missing on the first fragment. The fragment could not go through onDestroy if it comes back from the back-stack.

So it seems this solution might not work as intended. Does anyone have an idea for this?

@RaoulNL seems like you can use fragment.viewLifecycleOwner.lifecycle. Try that

@dav-true indeed, that solves the problem!