OneShotFieldDelegate.kt

import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

/**
 * getValue returns only once the exact value, in other cases [default] value will be returned
 */
private class OneShotFieldDelegate<T : Any?>(
    private val default: T,
) : ReadWriteProperty<Any?, T> {

    private var value: T? = null

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        val result = value ?: default
        value = default
        return result
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        this.value = value
    }
}

fun <T> oneShow(default: T): ReadWriteProperty<Any, T> = OneShotFieldDelegate(default)